Archivi tag: solar activity

Sunspot formation: theory, simulations and observations

Scientific recording of sunspots started with Galileo in 1609. Since Hale (1908) we know that sunspots are strong concentrations of magnetic field of up to 4000 gauss. They could be formed by subsurface magnetic flux tubes piercing the surface. Meanwhile, numerical simulations by many different groups suggest that strong magnetic fields could be generated in the bulk of the convection zone. This would mean that sufficiently strong magnetic fields may be generated not far from the surface. However, at the surface the magnetic field appears to be strongly concentrated into only a few isolated spots – in stark contrast to the more diffuse magnetic field beneath the surface. This is still a mystery.
Continua a leggere Sunspot formation: theory, simulations and observations

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EWASS 2013

Finland will attend the European Week of Astronomy and Space Science, which is going to be held on 8 – 13 July 2013 in Logomo Centre in Turku, Finland. EWASS is the annual meeting of the EAS. On Saturday, 13 July, is also the Plenary discussion on the ASTRONET Mid-Term Review that is closely connected to the EWASS meeting.

The programme for the EWASS 2013 has now been finalized, but small additions are still possible. The pdf-version of the programme with all the timetables and details can be downloaded here. We are going to print this for the meeting and you will have this during the registration.

Symposia

S1: Solar activity and its manifestations in the heliosphere (PI Rami Vainio)
S2: The physics of accretion on compact objects (PI Juri Poutanen)
S3: Science with Planck data (PI Pekka Heinämäki)
S4: The mystery of ellipticals (PI Peter Johansson)
S5: Local group, local cosmology (PI Matteo Monelli/Stefania Salvadori)
S7: Stellar magnetic activity across the HR diagram (PI Maarit Mantere)
S8: Deaths of massive stars as supernovae and gamma-ray bursts (PI Seppo Mattila)
S9: Extreme physics of neutron stars (PI Dmitry Yakovlev)
S10:The co-evolution of black holes and galaxies (PI Jari Kotilainen)
S11: Gaia research for European astronomy training (PI Nicholas Walton)
S12: The gamma-ray sky in the era of Fermi and Cherenkov telescopes (PI Tuomas Savolainen/Elina Lindfors)

Special sessions

Sp1: Astronomy education and public outreach (PI Mikko Hanski)
Sp2: RADIONET: “The role of modern radio observatories in black hole and jet studies” (F.Mantovani/T. Savolainen/M. Tornikoski)
Sp3: Fundamental stellar parameters (PI Luca Casagrande)
Sp4: The origin of interstellar dust (PI Patrice Bouchet)
Sp5: Thick discs: clues for galaxy formation and evolution (PI Sebastien Comeron)
Sp6: AGN, galaxy mergers, supermassive black holes and gravitational waves (PI Stefanie Komossa/Mauri Valtonen)
Sp7: Science with present and future interferometric instruments (PI Jean Surdej)
Sp8: Galactic molecular clouds and their chemistry (PI Mika Juvela)
Sp9: Stellar dynamics and celestial mechanics in modern astrophysics (PI Rainer Spurzem/Seppo Mikkola)
Sp10: Chemo-dynamical galaxy evolution (PI Gerhard Hensler)
Sp11: Rocks in our Solar System (PI Tomas Kohout)
Sp12: A fresh look at the stellar initial mass function (PI Ignacio Ferreras)
Sp13: Starburst galaxies now and then with ALMA (PI Jari Kotilainen)
Sp14: LOFT, the large observatory for X-ray timing (PI Enrico Bozzo)

Fifty Years of Seismology of the Sun and Stars

In the last 50 years, helioseismology has made significant contributions to the knowledge of the Sun’s interior physics and has led the way to asteroseismology. We have now reached an era where more sophisticated questions are being asked to understand the subtle properties of the Sun and other stars due to the synoptic and high-resolution observations available from BISON, GONG and space missions such as SOHO, SDO, CoRot and Kepler. On this occasion, a workshop on the theme of “Fifty Years of Seismology of the Sun and Stars” is being organized to discuss the advances, reflect on the progress that has been made, and address new challenges. We plan to bring together helio- and asteroseismologists, theorists and observers in a journey that will take us from the interior of the Sun and its magnetism towards the structure of distant stars and activity cycles.

Topics include:

  • Historical perspective
  • Advances in observational technique
  • Solar structure and dynamics
  • Stellar activity and variability
  • Local helioseismology and helioseismic imaging
  • Numerical simulations of convections and waves
  • Seismology of the solar atmosphere
  • Requirements for future instrumentation
  • Prospects for future missions

Does solar activity trigger earthquakes?

Credit: NASA
Credit: NASA

It seems no! Infact, geophysicists have disproved a long-held belief that changes in solar activity can be linked to increased earthquake activity.  Researchers at the United States Geological Survey (USGS) studied the different phenomena thought to prompt seismic activity. One theory is that a rise in solar activity, like sunspots, solar wind speed, or magnetic storms could trigger more, or larger, earthquakes.

Recently there’s been a lot of interest in this subject from the popular press, probably because of a couple of larger and very devastating earthquakes. This motivated us to investigate for ourselves whether or not it was true“, says Jeffrey Love from the USGS, lead author of the study. But when Love and his colleague, Jeremy Thomas from Northwest Research Associates, examined the relationship between peaks in solar activity and large earthquakes, they found there was no correlation at all. “There have been some earthquakes like the 9.5 magnitude Chile quake in 1960 where, sure enough, there were more sunspots and more geomagnetic activity than on average. But then for the Alaska earthquake in 1964 everything was lower than normal. There’s no obvious pattern between solar activity and seismicity, so our results were inconclusive“, Love says. The pair used data from the British Geological Survey, USGS, NASA and the National Oceanic and Atmospheric Administration to count the number of earthquakes per day, month and year. They then ranked these counts depending on how much solar-terrestrial activity had occurred at the same time. They showed that there are just as many earthquakes whether or not there is lots of solar activity. “From previous work we had found that ground sensors in the vicinity of earthquakes did not show any “precursory” signal that might be used to predict an earthquake. Still, some historical and some recent studies seemed to indicate a solar triggering of earthquakes, so we decided to investigate this as well“, explains Love. “One prominent claim was that there might be a relationship between the solar-terrestrial activity and the timing of the great Sumatra earthquake, so we looked at that specifically”, explains Love. The Sumatra earthquake occurred on boxing day in 2004 and had a magnitude of 9.3 – the third largest earthquake ever recorded. “But as far as we can tell the solar activity was perfectly normal and there is no reason to think normal conditions could cause more or bigger earthquakes”. The theory was first proposed in the late nineteenth century by Rudolf Wolf, a Swiss astronomer and mathematician known for his research into sunspots. Love understands why people might believe there is a correlation between the two phenomenon. “It’s natural for scientists to want to see relationships between things” he says. “Of course, that doesn’t mean that a relationship actually exists!

Planet Earth On Line: No link between solar activity and earthquakes

Geophysical Research Letters: Insignificant solar-terrestrial triggering of earthquakes