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PROPERTIES OF THE EXTREME SOLAR PARTICLE EVENTS DURING THE SOLAR CYCLES 22 & 23

PROPERTIES OF THE EXTREME SOLAR PARTICLE EVENTS DURING THE SOLAR CYCLES 22 & 23. Andriopoulou Maria (1), Mavromichalaki Helen (1), Plainaki Christina (2), Belov Anatoly (3),Eroshenko Eygenia (3). Physics Department, University of Athens, Greece

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PROPERTIES OF THE EXTREME SOLAR PARTICLE EVENTS DURING THE SOLAR CYCLES 22 & 23

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  1. PROPERTIES OF THE EXTREME SOLAR PARTICLE EVENTS DURING THE SOLAR CYCLES 22 & 23 Andriopoulou Maria (1), Mavromichalaki Helen (1), Plainaki Christina (2), Belov Anatoly (3),Eroshenko Eygenia (3) • Physics Department, University of Athens, Greece • IFSI-Istituto di Fisica dello Spazio Interplanetario, Roma, Italy • IZMIRAN Russian Academy of Sciences after Puskov, Moscow, Russia

  2. GLEs (Ground Level Enhancements) • SEPs with energy greater than 500MeV • Short and sharp increases in the counting rates of cosmic ray intensity • Penetrate inside Earth’s atmosphere and recorded by ground based detectors • Several modeling techniques analyze their characteristics • Each event seems to constitute a unique case, determined by current solar & interplanetary conditions • Involved in many scientific applications, such as: prediction of dangerous particle fluxes that may damage • satellites and telecommunications, analysis of interplanetary conditions, prediction of strong geomagnetic storms occurrence • A GLE-alert system recently developed in Athens neutron monitor station, with ability to provide the earliest alert possible for a SEP event onset (http://cosray.phys.uoa.gr)

  3. In order to investigate the existence of common physical mechanisms among GLEs a statistical analysis for the 11 most intense events of solar cycles 22 and 23 (1986-2007) is carried out. • GLE42:09.29.1989 • GLE43:10.19.1989 • GLE44:10.22.1989 • GLE45:24.10.1989 • GLE52:06.15.1991 • GLE59:07.14.2000 • GLE60:04.15.2001 • GLE65:10.28.2003 • GLE66:10.29.2003 • GLE69:01.20.2005 • GLE70:12.13.2006 For this analysis 5-min (mostly) & 1-min data used, provided from stations of the worldwide network of neutron monitors, collected and processed from the IZMIRAN group (ftp://cr0.izmiran.rssi.ru/COSRAY!/FTP_GLE/) as well as from the recently created real-time High resolution Neutron Monitor Database (NMDB) http://www.nmdb.eu.

  4. Analysis of each GLE included: • onset time calculation (using 1-min & 5-min data) for each NM observed the GLE, • maximum intensity rate identification and time it • was reached (5-min), • time-lag calculation between maximum amplitude time and onset time (5-min) • longitudinal distribution & latitudinal distribution for the maximum intensity of the event • longitudinal-latitudinal distribution for the event’s maximum intensity, for various altitudes • effort to connect GLEs with solar & geomagnetic phenomena, like solar flares (SF), coronal mass ejections (CMEs) and sudden storm commencements (SSCs)

  5. After an analytical study and comparison among the 11 events, some preliminary results of the analysis are presented. The most important GLE events during cycles 22 &23 as recorded from Oulu Distribution of the total cosmic ray intensity maximum during cycles 22 & 23 as recorded in Oulu station • The maximum annual record , for the Oulu NM, over ~21 years, took place at year 1989. • The GLE69 was the biggest one inside 22, 23 solar cycles. • The GLE44 was the most rapid ground level CR increase (reached maximum 5 min after the onset). • In 7 out of 11 GLE cases, the South pole NM station recorded the maximum increase.

  6. Preliminary results • An onset time variability among all neutron monitors that recorded the event of at least 10 minutes was recorded (using 5-min data). GLE43 & GLE69 remarkably anisotropic onset. GLE66 rather complicated. • All the events studied seem to be associated with an X-ray flare of class X, 63% of them west position and 54.5% of them south position. The most powerful flares don’t necessarily produce the most powerful GLEs. • All the events studied from solar cycle 23 seem to be associated with CME with linear speeds>882 km/sec. Lack of data for cycle 22. • There seem to be preferable directions for the registration of the significant GLEs. No yet an accurate determination of these regions. A more careful analysis needs to be made! The existence of a common data base, that includes a complete set of accurate data, such as the NMDB database is crucial for this kind of studies.

  7. Thank you

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