V. Yanke

Modeling ground level enhancements: Event of 20 January 2005

[1] The solar cosmic ray event associated with an X7.1 class solar flare on 20 January 2005 was one of the greatest enhancements ever recorded by the ground level worldwide network of neutron monitors. The event occurred during a Forbush decrease, almost at the end of the 23rd cycle of solar activity. In this work a ground level enhancement model for getting the broadest possible picture, as well as for understanding the physics of solar cosmic ray particles under extreme solar conditions, is proposed. Neutron monitors responses from 41 stations widely distributed around the Earth have been modeled to an anisotropic solar proton flux, using an optimization method based on the Levenberg-Marquardt algorithm. The parameters of the primary solar particles outside the magnetosphere and their dynamics, as well as the characteristics of solar cosmic rays during this event are obtained and discussed.

GLEs as a Warning Tool for Radiation Effects on Electronics and Systems: A New Alert System Based on Real-Time Neutron Monitors

Ground level cosmic ray enhancements (GLEs) are the manifestations of short-time solar energetic particles radiation near the Earth causing damage to electronic devices carried on board the satellite platforms. A test alert system based on a real-time ground-level neutron monitor network is proposed in order to protect devices and electronics from space weather radiation effects.

A New Version of the Neutron Monitor Based Anisotropic GLE Model: Application to GLE60

In this work we present a cosmic ray model that couples primary solar cosmic rays at the top of the Earth’s atmosphere with the secondary ones detected at ground level by neutron monitors during Ground-Level Enhancements (GLEs). The Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model constitutes a new version of the already existing NMBANGLE model, differing in the solar cosmic ray spectrum assumed. The total output of the model is a multi-dimensional GLE picture that reveals part of the characteristics of the big solar proton events recorded at ground level. We apply both versions of the model to the GLE of 15 April 2001 (GLE60) and compare the results.

Space weather forecasting at the new Athens center: the recent extreme events of January 2005

From the beginning of this year a new data analysis center [Athens Neutron Monitor Data Processing (ANMODAP) Center] is operated in Athens University producing a real-time prediction of space weather phenomena. At this moment there has been a multi-sided use of twenty-three neutron monitors providing real-time data on the Internet. Moreover, interplanetary space parameters data from Geostationary Orbiting Environmental Satellite and Advanced Composition Explorer (ACE) satellite are also collected in this center. The ANMODAP Center in real-time is of high potential interest, as it is expected to give alerts for ground level enhancements (GLEs) of solar cosmic rays (CRs) and geomagnetic storms and therefore to provide crucial information for Space Weather applications. Forecasting of the last GLE and the geomagnetic variations of CRs on January 2005, is presented.

ALERT SYSTEM FOR GROUND LEVEL COSMIC-RAY ENHANCEMENTS PREDICTION AT THE ATHENS NEUTRON MONITOR NETWORK IN REAL-TIME

The prediction of solar activity is important for various technologies, including operation of low-Earth orbiting satellites, electric power transmission grids, high-frequency radio-communications etc. The Athens Neutron Monitor Network in Real Time, initiated in December 2003, provides data from twenty-one real-time neutron monitor stations, useful for real-time monitoring of cosmic particle fluxes. Recently a program for forecasting the arrival of dangerous middle energy particles on the Earths surface has started. These program processes the data taken from the Neutron Monitor Network and informs us about the onset of ground level enhancements. In this way enough time to protect technological systems will be given.

Behavior of the cosmic-ray vector anisotropy before interplanetary shocks

The behavior of the galactic cosmic ray density and vector anisotropy during geomagnetic storms with sudden storm commencements has been investigated based on the global survey data. It is shown that the average anisotropy significantly increases directly before a sudden storm commencement; the larger the subsequent Forbush decrease, the larger the increase in anisotropy. The averaged values of the CR anisotropy and density start to be affected by the shock wave approximately 5 h before its arrival. Changes in the anisotropy direction (especially for west Forbush sources) can be observed much earlier.

The first Forbush decrease of solar cycle 24

The first significant Forbush decrease of solar cycle 24 was recorded in February 18, 2011 from neutron monitors around the world. This was the result of the coronal mass ejections (CMEs) that was released from the Sun on 14 and 15 February 2011, respectively, and their interplanetary counterparts (ICME) that were prevalent in the interplanetary space in this period. We report on the global characteristics of cosmic rays during the FD such as the amplitude (A0), the decrement and the three dimensional anisotropy parameters (Ax, Ay and Az), deduced from the global survey method (GSM). We also analyze the interplanetary space solar wind data and we present the structure of the ICME as it passed through the Earth resulting in a strong Forbush decrease. We compare high time resolution neutron monitor data with multipoint space-based measurements of the interplanetary space (e.g. ACE/SWEPAM and ACE/MAG).

Modeling of the solar energetic particles recorded at Neutron Monitors

Last year the worldwide network of neutron monitors recorded a new ground level enhancement (GLE) of cosmic my intensity (CR) on 20th of January 2005, during the recovery phase of a series of Forbush effects taking place at a time‐period very close to the minimum of the current cycle of solar activity. This enhancement seems to be the greatest GLE of the current solar cycle, reaching almost 5000% in some polar stations. A joint analysis of data from ground level stations (neutron monitors) and satellite measurements has been performed in order to calculate the amplitude and the anisotropy of the event as well as the energy of the more fast particles arriving at the Earth. A new GLE — model has been created in order to couple the primary solar cosmic ray flux on the top of the magnetosphere with the flux recorded by neutron monitors and define this way the primary solar cosmic ray spectrum during the event. Moreover, the absorption length of solar energetic particles propagating through the Earth’s atmosphere has been calculated applying the Wilson et al. method (1967). These results have been compared with the respective results calculated for other ground level enhancements. Finally, a comparison between this enhancement and the big GLE of 1956 has been performed.Last year the worldwide network of neutron monitors recorded a new ground level enhancement (GLE) of cosmic my intensity (CR) on 20th of January 2005, during the recovery phase of a series of Forbush effects taking place at a time‐period very close to the minimum of the current cycle of solar activity. This enhancement seems to be the greatest GLE of the current solar cycle, reaching almost 5000% in some polar stations. A joint analysis of data from ground level stations (neutron monitors) and satellite measurements has been performed in order to calculate the amplitude and the anisotropy of the event as well as the energy of the more fast particles arriving at the Earth. A new GLE — model has been created in order to couple the primary solar cosmic ray flux on the top of the magnetosphere with the flux recorded by neutron monitors and define this way the primary solar cosmic ray spectrum during the event. Moreover, the absorption length of solar energetic particles propagating through the Earth’s atmosph...

Modeling the behavior of the cosmic ray density in magnetic clouds

Our study focuses on the behavior of the density of cosmic ray particles at 10 GV rigidity in a magnetic cloud at Earth. It is shown that it can be mostly described by a simple parabolic dependence over distance from the centre of the cloud, when measured in gyroradii. The majority of magnetic clouds modulate cosmic rays, decreasing their density. However, there is a group of events (about 1/5 part of the total sample) during which the cosmic ray density increases within the magnetic cloud. The factors that contribute to the model description are considered, and estimates of their influence are carried out and discussed.

Magnetospheric cut-off rigidity variations recorded by neutron monitors in the events from 2001 to 2010

During a geomagnetic storm, many interesting variations in cosmic ray intensity recorded by the worldwide network of neutron monitor stations are observed. More specifically, a characteristic increase of cosmic ray intensity mainly in the middle latitude stations is observed, due to the geomagnetic cut-off rigidity changes. During the declining phase of the last solar cycle, many characteristic geomagnetic effects were observed with the most significant one on November of 2003, which is considered as the largest magnetic storm in the history of neutron monitors. In this work, the magnetic storms of 31 March 2001, 11 April 2001, 8 and 10 November 2004, 15 May 2005 and 24 August 2005 are analyzed using cosmic ray data from a number of neutron monitor stations located at different places worldwide.