Solar eclipse in St Andrews – Yes, we saw it!

The day had come; the 20th March was the day people all around Europe had been waiting for, the day of the solar eclipse. For most of the people, this is a once-in-a-lifetime event. To see an almost total eclipse is a very exciting thing! The Moon passing in front of the Sun, covering its full disk happened this time too, however only the lucky few were able to see it from the scene, since the track of the totality covered mostly the Norwegian Sea.

In St Andrews we were watching the weather forecast since Monday, to see how the weather changes; if we would have a nice, clear sky on Friday, even though we knew the weather here changes from hour to hour, making it impossible to predict it properly days before the event. It didn’t seem good, especially at the beginning of the week. By Thursday it cleared up a bit, however, by the end of the day new clouds covered the sky.

The crowd of excited people in front of the PandA building (Credit: Wendy Clark)

The crowd of excited people in front of the PandA building (Credit: Wendy Clark)

Where did the Sun go? A minute ago it was still here! -- No worries, we found it! (Credit: Wendy Clark)

Where did the Sun go? A minute ago it was still here! — No worries, we found it! (Credit: Wendy Clark)

On the morning of the solar eclipse, half an hour before the event, it was still pending if we would be able to see it: half of the sky (towards the east), was cloudy, while the other half was clear. But we were optimistic. Some of the enthusiastic PhD students and stuff members set up three telescopes in front of the Physics and Astronomy (PandA) building of the University of St Andrews. The two 8 cm telescopes (Meade ETC 80) were equipped with solar filters and cameras, one of which was connected to a tablet. The third telescope (Maksutov-Cassegrain, ~8 cm) was an older set up: it projected the Sun on a white plate (projection screen). We were ready for the big event.

And we were lucky! The sky cleared up! The clouds only bothered for a couple of minutes. We saw the eclipse from the beginning to the end. In St Andres the Moon covered about 95% of the Sun, which resulted in a slightly darker daytime around the maximum of the eclipse. It started at 8.31 with maximum at 9:36 finishing at 10:45. The event drew the attention of the public too. Families with children, students and stuff members, residents of the town came along to watch the eclipse with us. At some point a TV screen appeared, which was connected to the other camera, satisfying the popular demand.

The Maksutov-Cassegrain telescope in action. (Credit: Wendy Clarke)

The Maksutov-Cassegrain telescope in action. (Credit: Wendy Clark)

At the meantime, the totality was streamed in one of the lecture theatres inside the building. By the time the Moon covered the full disk of the Sun, the lecture theatre was crowded by people, who were about to see what the visitors and inhabitants of Svalbard could see: a beautiful diamond ring around the fully covered Sun.

Eclipse starting, with a 'tiny' sunspot on the bottom right third of the Sun. (Credit: Josh Argyle, Gabriella Hodosán, Milena Pawlik, Gabriella Hodosan, Victor See, David Starkey  (Astronomy PhD students of the University of St Andrews))

Eclipse starting, with some clouds and a ‘tiny’ sunspot on the bottom right third of the Sun. (Telescope: Meade ETC 80 mm refractor, Camera: Canon EOS 1100D) (Credit: Josh Argyle, Gabriella Hodosán, Milena Pawlik, Gabriella Hodosan, Victor See, David Starkey (Astronomy PhD students of the University of St Andrews))

The event was successful. The weather was kind to us, we had a sunny, warm morning, perfect for eclipse watching. The next eclipse, with similar (>90%) coverage will be visible from the UK in 2026.

Solar eclipse seen from St Andrews. (Credit: Josh Argyle, Milena Pawlik, Gabriella Hodosan, David Starkey (observing and photography), Victor See (editing))

Solar eclipse seen from St Andrews.
(Credit: Josh Argyle,  Gabriella Hodosán, Milena Pawlik, Victor See, David Starkey (Astronomy PhD students of the University of St Andrews))

 

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Electrification in dusty atmospheres inside and outside the solar system, Pitlochry, 8-11 Sep. 2014

The workshop ‘Electrification of dusty atmospheres inside and outside the solar system’ hosted by the LEAP Group took place in Pitlochry, Scotland. The cross-disciplinary nature of the workshop attracted scientists from fields of plasma physics, volcanology, meteorology, and astrophysics from all over the world.

The meeting started with a welcome barbeque on Sunday evening: people were talking in small groups, catching up with old friends and meeting new colleagues.

The welcome barbeque in the garden of the hotel

_DSC1519 The welcome barbeque in the garden of the hotel (Credit: Rubén Asensio Torres)

On Monday morning Christiane Helling summarized the scientific idea that lead to the organization of this workshop: she talked about the benefits of the meeting for both astrophysicists and scientists from other fields. She also introduced a new proceeding idea, which is planned to be published in Surveys of Geophysics.

The first talk was given by Alan Phelps who discussed laboratory studies of crystalline-like ordered structure in dense dusty plasmas, with the potential to investigate similar behaviour in substellar atmospheres. In this context, the exciting possibility exists of identifying a unique observable signature associated with plasma crystals that could be used to diagnose the charged environment.

The difficulties of the inter-disciplinary nature of the workshop appeared right after the first talk when it turned out that the definition of ‘dust’ is not the same in every field. However, after discussing the issue, the speakers and participants quickly got used to the fact that most of the people are from a different field than they are and explained their fields in a way, which was understandable for everyone.

Keri Nicoll and Corrado Cimarelli gave exciting talks on volcanic lightning. Nicoll gave an overview on the different charging mechanisms in volcanic plumes and reported that broad particle size distributions of volcanic ash clouds are more susceptible to triboelectric charging, which give an analogy to substellar clouds with atmospheric regions with the appropriate particle size distribution. Cimarelli described a laboratory experiment where they reproduced volcanic lightning strikes, and explained how the particle size and distribution affects the charge separations on plumes.

Euan Bennet’s talk on isolating different sized bacteria using electrostatic disruption of water droplets was an interesting part of the conference. It showed some of the unexpected applications that can arise from the study of aerosol electrification.

During the afternoon session Ute Ebert introduced us into the mechanism of lightning development and gave an overview of streamer propagation. The following talks were about Transient Luminous Events (TLEs) such as sprite modelling and the possibility of TLE initiation on gas giant planets like Jupiter.

The afternoon ended with the poster pop-up, where each poster presenter was given one minute to advertise his or her work, which was followed by the poster session itself. Delicious pretzels and Guinness accompanied the session.

_DSC1609

_DSC1623 Poster session (Credit: Rubén Asensio Torres)

On Tuesday we started with a very interesting talk by Farideh Honary on Lunar dust charging and how this can affect future (and past) landing missions. Karen Aplin introduced us a similar approach but with asteroids. She raised the question of what would happen if a, possibly, oppositely charged landing spacecraft (negatively charged) and the surface of an asteroid (positively charged) interact with each other and showed a model of how the electrostatic effects can be best measured in situ.

The afternoon session started with Ian Dobbs-Dixon’s presentation on dynamical modelling of the atmospheres of tidally locked hot Jupiters. Michael Rycroft introduced the audience to the conditions a planet would need in order to host a global electric circuit.

In the evening we had the workshop dinner in the hotel. In a short dinner speech, Christiane Helling also thanked all the participants for their exciting contributions to the workshop. Towards the end of the dinner Craig Stark announced the winners of the poster contest, Graham Lee and Karen Aplin. Congratulations!

Wednesday was the day of brown dwarfs (BDs) and ionization processes. Sara Caswell talked about two White Dwarf–Brown Dwarf systems and showed how different the spectra of the day and night side of an irradiated BD can be. Irena Vorgul gave a talk on how flash ionization processes (such as lightning) could be detected through cyclotron maser emission going through the affected atmospheric volume. Craig Stark summarized the concept of the LEAP Project, then talked about the basics of Alfvén ionization, a process where a low density magnetized plasma is hit by a high speed flow of neutral gas. He then talked about the possibility of creating prebiotic molecules (like glycen) on the surface of dust particles in plasmas. An impressive talk was given by Takayuki Muranushi, how proposed to use ion lines width for detection lightning occurring within protoplanetary disks.

On the last day of the workshop we learnt a lot about cosmic ray (CR) air showers and their ionizing effects. However, due to a change in the schedule, the first talk was about multi-wavelength observations of BDs given by Stuart Littlefair. He showed that consistent cyclotron emission detection shows very good correlation with optical observations, suggesting an aurora-like mechanism for the radio emission. There is though some variation in radiated power for different periods of rotation, which might also be attributed to undergoing transient processes in the atmosphere (like lightning).

Alan Watson talked about the work at the Pierre Auger Observatory, an ultra-high-energy CR detector in Argentina. He showed us an unusual phenomenon observed by multiple detectors and asked the opinion of the audience on the topic. Large variety of ideas came including possible lightning events, and military missile activity as well. Although the question has not been answered unequivocally, the response from the audience showed how beneficial such a multi-disciplinary meeting can be for the different scientific fields. Paul Rimmer went into the details of CR ionization in BD atmospheres and proposed the possibility of using Jupiter as a giant gamma-ray detector through the extensive CR air showers occurring in its atmosphere.

The last talk of the day and the workshop was given by Scott Gregory who showed us how stellar magnetic fields can affect the habitability of a planet orbiting that star. He also pointed out that the magnetic field structures differ for different stars.

The afternoon was rounded off with a whiskey tour and tasting in the Blair Atholl Destillery where we learnt a lot on how whiskey is made, what are the main ingredients, how is the alcohol content regulated and how much time the infusion spends in the barrels.

A few of the participants had the opportunity to tour the Blair Castle and its extensive grounds on Friday. The fresh apples and pears from the trees in the Hercules garden were especially enjoyable.

On the whole the workshop was a great experience for all of us, the talks were very diverse still related to our work in the LEAP Group. All speakers made great efforts to allow the audience to appreciate their contribution to the workshop’s theme. We had a great opportunity to meet scientists from other fields and discuss our projects, concerns, works with them.

We would like to thank all of the participants for their contribution to the success of the workshop. The high quality of the talks and posters gave an insight for the audience into the different disciplines.

 

Participants of the workshop (Credit: Rubén Asensio Torres)

Participants of the workshop (Credit: Rubén Asensio Torres)

Lightning on exoplanets and brown dwarfs: How extended and energetic could these events be?

Lightning events are very spectacular phenomena on Earth. They are one of those beautiful plays of nature, which interest both scientists and non-scientists equally. But can lightning occur on objects outside our Solar System? The St Andrews student Rachel Bailey studies the scales that large-scale gas discharges can develop, what atmospheric volume might be affected, and what amount of energy may be deposited into the atmospheres of brown dwarfs and planets under the supervision of Dr Christiane Helling. This study was performed in collaboration with Gabriella Hodosán, Camile Bilger and Craig Stark.

Lightning strike above the Arabian Peninsula captured from aboard the ISS. (Credit: NASA)

Fig. 1. Lightning strike above the Arabian Peninsula captured from aboard the ISS. (Credit: NASA)

Atmospheric electrical discharges (like lightning) are observed not only on Earth. Lightning on Jupiter was observed both in optical and radio wavelengths of the electromagnetic spectrum. In the late ‘70s early ‘80s the Voyager 1 spacecraft recorded impulsive events in the radio band which were called SEDs or Saturnian Electrostatic Discharges. These events were identified as lightning discharges, although the optical confirmation did not come until 2009. Electromagnetic signatures associated with lightning activity were also detected on Uranus and Neptune by Voyager 2.

Lightning activity on Saturn captured by NASA’s Cassini Spacecraft. For the animated version check out Space.com  (Credit: NASA/ JPL-Caltech/ SSI/ University of Iowa)

Fig. 2. Lightning activity on Saturn captured by NASA’s Cassini Spacecraft. For the animated version check out Space.com (Credit: NASA/ JPL-Caltech/ SSI/ University of Iowa)

Not all processes involved in lightning are known in detail. The simplest idea is the following: first, a strong electric field needs to be present for long enough. This electric field, or potential difference, builds up by various ionisation processes. Processes like particle encounters with cosmic rays would make the electrons break away from their ‘parent’ atom or molecule, which leads to the formation of negative and positive ions and the atmospheric gas becomes conductive. Second, a large-scale separation of these charges over large enough distances is needed. One process causing large-scale charge separation is gravitational settling (also known as‘rain’). If the distance between the charged cloud layers is large enough, the electric field can grow so strong that it exceeds a threshold, which results in the acceleration of electrons to very high energies. These energetic electrons will ionise their surroundings by freeing more electrons resulting in an avalanche of high-energy electrons and, as a final step, a lightning discharge. This process is called runaway breakdown.

Charge separation and different types of lightning discharges (inter- and intra-cloud, and cloud-to-ground discharges) (thunder.msfc.nasa.gov/primer)

Fig. 3. Charge separation and different types of lightning discharges (inter- and intra-cloud, and cloud-to-ground discharges) (thunder.msfc.nasa.gov/primer)

Other interesting phenomena related to lightning activity are Sprites. Sprites appear above thunderclouds as extended red discharges, right after a lightning strike. These luminous events on Earth can be observed from space.

It is very likely that lightning also occurs outside the Solar System. Both exoplanets and brown dwarfs host clouds, which are made of minerals or gemstones. Why is it important to know how extended and energetic lightning events are on extrasolar bodies of interest? First, lightning affects the local chemistry of the atmosphere creating molecules that otherwise would not appear, such as prebiotic molecules responsible for the origin of life on the young Earth. On the other hand it is of interest to know whether the discharge energy is large enough to be detectable from Earth.

Atmospheres of cool objects (brown dwarfs and gas giant planets with global temperatures between 500 and 2700 K) are cold and dense enough for mineral clouds to condense. In this paper we adopt the idea that a large-scale discharge is initiated by an electron avalanche that develops into a streamer (electrically conducting channel). We apply our discharge-propagation model to one-dimensional Drift-Phoenix atmosphere models, which provide information about the local gas temperature, pressure and chemical composition.

Streamer properties in laboratory experiments as used in this paper: the segment length, L, is the length of a single segment of the streamer. The minimum diameter, dmin, is the minimal segment diameter as streamer can reach. The energy per length is the amount of dissipated energy per length of single segment. (Briels, T. M. P. et al. 2008, JPhD, 41, 234008; ©IOP Publishing. Reproduced with permission. All rights reserved.)

Fig. 4. Streamer properties in laboratory experiments as used in this paper: the segment length, L, is the length of a single segment of the streamer. The minimum diameter, d_min, is the minimal segment diameter as streamer can reach. The energy per length is the amount of dissipated energy per length of single segment. (Briels, T. M. P. et al. 2008, JPhD, 41, 234008; ©IOP Publishing. Reproduced with permission. All rights reserved.)

 Our analysis shows that the electrical breakdown can occur inside the cloud layer (lightning) and/or above the cloud layer (sprite). From these locations the discharge propagates through the atmosphere while subsequent branches appear until it reaches a minimum diameter and the discharge terminates.

Our results show that a lightning strike reaches longer distances in a brown dwarf than in an exoplanet, which means it affects larger atmospheric volumes in the former than in the latter. The total energy that dissipates from one such event is less then 1012 J. (For comparison, on Jupiter and Saturn this value is around 1012-1013 J while on Earth it is ~108-109 J.) This energy causes an increase in the local gas temperature, which results in changes in the local chemistry as well. In the paper we showed the increase of small carbohydrate molecules such as CH and CH2.

Total lengths, L_discharge, that a large-scale discharge can reach in different atmospheres (left), and total dissipated energy for different model atmospheres (right) (top panels – giant gas planet, bottom panels – brown dwarf). Solid lines indicate solar metallicity, dashed lines show sub-solar metallicity. Left: results for two different value of a constant number of charges (Q). (Bailey et al. 2014, Fig. 9, Fig 11.)

Fig. 5. Total lengths, L_discharge, that a large-scale discharge can reach in different atmospheres (left), and total dissipated energy for different model atmospheres (right) (top panels – giant gas planet, bottom panels – brown dwarf). Solid lines indicate solar metallicity, dashed lines show sub-solar metallicity. Left: results for two different value of a constant number of charges (Q). (Bailey et al. 2014, Fig. 9, Fig 11.)

Considering mineral clouds, the closest alternatives on Earth we can investigate are volcano plumes, which are composed of small silicate ash particles. After explosive eruptions, volcano plumes host lightning activity that is orders of magnitudes larger than in a common thundercloud on Earth. Taking these arguments into account it is suggested that we provided a lower limit of the dissipation energy and that, in reality lightning can be stronger and more frequent on fast rotating extrasolar objects.

Volcanic lightning captured over the Puyehue-Cordon Caulle volcanic chain in southern Chile on 4 June, 2011. (Credit: Francisco Negroni/Agenciauno /EPA)

Fig. 6. Volcano lightning captured over the Puyehue-Cordon Caulle volcanic chain in southern Chile on 4 June, 2011. (Credit: Francisco Negroni/Agenciauno /EPA)

For more details check out the original paper on ADS:

R. L. Bailey, Ch. Helling, G. Hodosán, C. Bilger & C. R. Stark 2014, ApJ, 784, 43.

Also look at the University press release of the paper:

http://www.st-andrews.ac.uk/news/archive/2014/title,242028,en.php

Christiane Helling gives a press conferenc on 30 April, 2014 (9 am):

 http://client.cntv.at/EGU2014/?play=31

The LEAP Group can be found here:

http://leap2010.wp.st-andrews.ac.uk/

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Aurora Borealis – The play of colours over St Andrews

During the night of 27 February, 2014 a rare phenomenon took place on the sky of St Andrews. Around 10 pm the lucky ones saw the amazing red and green splendour of the Aurora.

IMGP3755

Red and green lights of the Aurora Borealis with the Castle of St Andrews in the front. (Credits go for Pasquale Galianni, astronomer of the University of St Andrews)

Red and green lights of the Aurora Borealis with the Castle of St Andrews in the front. (Credit: Pasquale Galianni)

Everyone heard of the bright, dancing, colourful lights of the Aurora Borealis. Some have seen it by their own eyes, others have seen breathtaking pictures of it. But what is the Aurora exactly?

The Northern Lights are natural light phenomena, which occur at high latitudes on both hemispheres of the Earth (called Aurora Borealis on the North and Aurora Australis on the South). It is the result of the collisions of charged particles coming from the Sun as solar wind and the upper part of a planet’s atmosphere.

In the upper corona of the Sun the velocity of the thermal motion of the particles become higher than the escape velocity. This results in a continuous material loss from the Sun in the form of solar wind. These charged particles (ions and electrons) hit the Earth’s magnetosphere and tie to it. The magnetosphere accelerates some of these particles towards the Earth’s surface. As they reach the upper atmosphere they collide with atoms and molecules releasing kinetic energy, which we is seen as the lights of the Aurorae. The more active the Sun (which means more solar wind) the more frequent the Aurorae.

The colour of the lights depends on the atom/molecule the energetic particle collides with. The most commonly seen type is the green Aurora. At mid altitudes (~ 100 km), where the concentration of oxygen atoms is fairly high, the collisions between atoms and ions/electrons releases energy at ~560 nm, which is in the green part of the spectrum. At the highest altitudes (up to ~300 km) the oxygen atoms emit around 630 nm (red part of the spectrum). Because of the lower concentration of the atoms in this part of the atmosphere, red Aurorae are seen very rarely and only when the Sun is around its activity maximum. The blue colour is the result of the collision with molecular nitrogen. This takes place at lower altitudes, where the amount of atomic oxygen is reduced.

Aurora Borealis seen from the Observatory of St Andrews. (Credit: Diana Juncher)

Aurora Borealis seen from the Observatory of St Andrews. (Credit: Diana Juncher)

The Aurora is not unique on Earth in the Solar System. Planets like Jupiter or Saturn, which have stronger magnetic fields than Earth exhibit even more spectacular light phenomena. Auroral light was observed on Uranus and Neptune as well.

The Northern Light we saw last Thursday was the result of a very energetic solar flare which was erupted on the 25 Feb (00:25 UTC). NASA’s Solar Dynamics Observatory (SDO) captured the gigantic flare in different wavelengths. The one seen below is a composite image of two wavelengths of extreme ultraviolet light (171 and 304 Angstroms). The flare is classified as X4.9 which means it is one of the most powerful types. As the Coronal Mass Ejection (CME) originated from this flare reached the Earth’s magnetosphere the beautiful dance of lights appeared on our sky.

Solar flare erupted on at 00:25 (UTC) 25 Feb as capured by the SDO. This image is the combination of two wavelengths of extreme ultraviolet light (171 and 304 Angstroms). (Credit: NASA/SDO)

Solar flare erupted on at 00:25 (UTC) 25 Feb as capured by the SDO. This image is the combination of two wavelengths of extreme ultraviolet light (171 and 304 Angstroms). (Credit: NASA/SDO)

And to finish with, here is a nice GIF made from some of Diana’s photos. Thanks to Inna Bozhinova for creating this short “movie” for us!

Aurora Borealis on the 27 Feb. (Credit: Diana Juncher, Inna Bozhinova)

Aurora Borealis on the 27 Feb. Click on the image to see it in a better quality. (Credit: Diana Juncher, Inna Bozhinova)

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