[Russian version]

 

M a i n    p a g e

Future  seminars

P a s t  seminars

Seminar council

 

FUTURE SEMINARS,  2013

 

December, 2

Vladimir Rakov (University of Florida, Institute of Applied Physics of the RAS)

"Compact Intracloud Lightning Discharges"

Abstract:

Compact Intracloud Lightning Discharges (CIDs), which were first reported by Le Vine (1980), received their name (Smith et al. 1999) due to their relatively small (hundreds of meters) spatial extent. They
are most intense natural producers of HF-VHF (3 300 MHz) radiation on Earth,
tend to occur at high altitudes (mostly above 10 km),
appear to be associated with strong convection, however, even the strongest convection does not always produce CIDs,
tend to produce less light than other types of lightning discharges (no hot channel?),
produce single bipolar electric field pulses (Narrow Bipolar Pulses or NBPs) having typical full widths of 10 to 30 μs and amplitudes of the order of 10 V/m at 100 km, which is comparable to or higher than for return strokes in cloud-to-ground (CG) flashes.
The mechanism of electromagnetic radiation of CIDs and their parameters will be presented and discussed.

 

November, 19

Leopold Lobkovsky (P.P.Shirshov Institute of Oceanology RAS)

"Geological evolution and present lithosphere state of Arctic: field investigations, theoretical models and practical applications"

 

September, 20

N. Vedenkin, S. Ivanov (Dauria Aerospace)

"Dauria Aerospace microsatellites"

 

September, 17

Joerg Buechner (Max Planck Institute for Solar System Research)

"Magnetic reconnection at the Sun"

 

September, 10

Irina Kitiashvili (Stanford University, Kazan University)

"Turbulent MHD processes at the Sun "

 

June, 27

Carl Gwinn (University of California, Santa Barbara)

"RadioAstron Pulsar Early Science Results"

Abstract:

The early science program for the RadioAstron mission has produced remarkable results for pulsars. Using baselines as long as 220,00 km, we locate the material that scatters nearby pulsars, only 2-8 pc from Earth. Observations of more distant, highly-scattered pulsars show fringes on baselines of tens of Earth diameters, where scattering should lead to zero average visibility. We discuss possible interpretations of this result.

 

June, 17

Salvatore Capozziello (University of Napoli Federico II)

"Scaling Relations from Gamma Ray Bursts to constrain Cosmography"

Abstract:

Relations connecting gamma ray burst quantities can be used to constrain cosmographic parameters of the Hubble law at medium-high redshifts. We consider a sample of gamma ray bursts to construct the luminosity distance to redshift relation and derive the values of the parameters q_0, j_0, and s_0. The analysis is compared with other methods in the literature. Gamma ray bursts, if calibrated by SNeIa, seem reliable as distance indicators and give cosmographic parameters in good agreement with some Dark Energy models.

 

June, 13

Michael S. Briggs (The Center for Space Plasma and Aeronomic Research, Huntsville, USA)

"Observations of Terrestrial Gamma-ray Flashes (TGFs) by the Fermi Gamma-ray Burst Monitor (GBM)"

 

Abstract with references:

 

Observations of Terrestrial Gamma-ray Flashes (TGFs) by the Fermi Gamma-ray Burst Monitor (GBM)

 

TGFs have were discovered in the early 1990s and since then have been observed with several astrophysical instruments, most recently with the Gamma-ray Burst Monitor (GBM) on Fermi. With the large effective area of GBM new properties of the pulses have been found: in addition to the previously known muliple pulses with ms separations, very close pulses are observed [1,4]. The GBM sample has two pulse types; also, the rise time is aways equal to or shorter than the fall time [1]. A new GBM datatype and TGF search method has been implemented, making GBM the instrument with the highest TGF detection rate [7]. In addition to fainter TGFs, GBM is detecting TGFs shorter than ever before detected, with durations as short as 50 microseconds [7]. Some TGFs are observed at great distances from the source when electrons follow the Earth's magnetic field in a beam. GBM found these Terrestrial Electron Beams (TEBs) to also contain positrons [2]. Correlation of GBM TGFs with ground-based radio observations has revealed new features [3,5,6]. A strong correlation between radio detection probabilty and gamma-ray duration changed our interpretation of the VLF radio detections, showing that they are of the current of the TGF itself [6].

 

preprints: http://gammaray.nsstc.nasa.gov/publications/tgf_journal.html

 

[1] First Results on Terrestrial Gamma-ray Flashes from the Fermi Gamma-ray Burst Monitor, M. S. Briggs, G. J. Fishman, V. Connaughton, et al., J. Geophys. Res. (2010).

[2] Electron-Positron Beams from Terrestrial Lightning Observed with Fermi GBM, M. S. Briggs, V. Connaughton, C. A. Wilson-Hodge, et al., Geophys. Res. Lett (2010).

[3] Associations between Fermi GBM Terrestrial Gamma-ray Flashes and sferics from the WWLLN, V. Connaughton, M. S. Briggs, R. H. Holzworth, et al., J. Geophys. Res. (2010).

[4] Temporal properties of the terrestrial gamma-ray flashes from the Gamma-Ray Burst Monitor on the Fermi Observatory, G. J. Fishman,, M. S. Briggs, V. Connaughton, et al., J. Geophys. Res. (2011).

[5] The lightning-TGF relationship on microsecond timescales, S. Cummer, G. Lu, M. S. Briggs, et al., Geophys. Res. Lett (2011).

[6] Radio signals from electron beams in Terrestrial Gamma-ray Flashes, V. Connaughton, M. S. Briggs, S. Xiong, et al., J. Geophys. Res. (2012).

[7] Terrestrial Gamma-ray Flashes in the Fermi era: Improved Observations and Analysis Methods, M. S. Briggs, S. Xiong, V. Connaughton, et al., J. Geophys. Res. (2013).

 

Michael S. Briggs

National Space Science & Technology Center

Principal Research Scientist

University of Alabama in Huntsville

Gamma-Ray Astronomy Group

320 Sparkman Drive

The Center for Space Plasma and Aeronomic Research (CSPAR)

Huntsville, AL 35805

Michael.Briggs@uah.edu or Michael.S.Briggs@nasa.gov

256-961-7667

 

April, 30

A.P. Itin (Institut für Laser-Physik, Hamburg, Germany; Zentrum für Optische Quantentechnologien (ZOQ), Hamburg, Germany; Space Research Institute (IKI), Moscow)

"Bose-Einstein condensates: fundamental applications on the Earth and in space. Projects QUANTUS, PRIMUS, MAIUS, ZARM"

 

April, 26

1. Weiqun Gan (the Purple Mountain Observatory, Nanjing, China)

"Frequency Distribution of Solar Flares"

2. Li Feng (the Purple Mountain Observatory, Nanjing, China)

"Magnetic energy partition between a CME and a flare from AR 11283"

Abstracts:

1. Before the formal talk, I would like to take a few minutes to give a brief introduction of solar community in China and PMO. Then I will focus on our recent work on frequency distribution of solar flares: the scaled peak distribution of GOES flares; the thermal energy distribution of flares; a fitting study of the flare distribution.

2. On 2011 September 6, an X-class flare and a halo coronal mass ejection (CME) were observed from Earth erupting from the same active region AR 11283. The magnetic energy partition between them has been investigated. SDO/HMI vector magnetograms were used to obtain the coronal magnetic field using the nonlinear force-free field (NLFFF) extrapolation method. The free magnetic energies before and after the flare were calculated to estimate the released energy available to power the flare and the CME. For the flare energetics, thermal and nonthermal energies were derived using the RHESSI and GOES data. To obtain the radiative output, SDO/EVE data in the 0.1-37 nm waveband were utilized. We have reconstructed the three-dimensional (3D) periphery of the CME from the coronagraph images observed by STEREO-A, B, and SOHO. The mass calculations were then based on a more precise Thomson-scattering geometry. The subsequent estimate of the kinetic and potential energies of the CME took advantage of the more accurate mass, and the height and speed in a 3D frame. The released free magnetic energy resulting from the NLFFF model is about 6.4 × 1031 erg, which has a possible upper limit of 1.8 × 1032 erg. The thermal and nonthermal energies are lower than the radiative output of 2.2 × 1031 erg from SDO/EVE for this event. The total radiation covering the whole solar spectrum is probably a few times larger. The sum of the kinetic and potential energy of the CME could go up to 6.5 × 1031 erg. Therefore, the free energy is able to power the flare and the CME in AR 11283. Within the uncertainty, the flare and the CME may consume a similar amount of free energy.

 

April, 18

L. Rykhlova (INASAN)

"Chelyabinsk meteorite and asteroid and cometary hazard"

Abstract:

Chelyabinsk meteorite entered Earth' s atmosphere at about 9-20 YEKT with estimated speed of 18 km/s. The total kinetic energy before atmospheric impact equivalent to approximately 450-500 kilotons of TNT. The object had not been detected before atmospheric entry.