Decrease of Schumann resonance frequencies and changes in the effective lightning areas toward the solar cycle minimum of 2008–2009

<p>Employing a set of 3-component search coil magnetometer, Schumann resonance studies have been in progress at Agra (Geograph. lat. 27.2°N, long. 78°E), India since 01 April, 2007. We have analysed the data for two periods; first from 01 April, 2007 to 31 March, 2008 (period-I), and then from 01 March, 2011 to 29 February, 2012 (period-II) which correspond to pre and post periods of solar cycle minimum of 2008-2009. From the diurnal variation of first mode intensity and frequency, we study the seasonal variations of global thunderstorm activity, effective source distance and level of lightning during both the periods. We show that world thunderstorm activity shifts to summer in the northern hemisphere as the effective source distance approaches close to the observer, and the level of intense lightning shifts from the month of July, 2007 in period-I to August, 2011 in period-II. This is supported by Lightning Imaging Sensor (LIS) satellite data also. A possible explanation in terms of increasing solar activity is suggested.</p>

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A significant decrease of the fundamental Schumann resonance frequency during the solar cycle minimum of 2008-9 as observed at Modra Observatory

Contributions to Geophysics and Geodesy ◽

10.2478/v10126-009-0013-5 ◽

2009 ◽

Vol 39 (4) ◽

pp. 345-354 ◽

Cited By ~ 4

Author(s):

Adriena Ondrášková ◽

Sebastián Ševčík ◽

Pavel Kostecký

Keyword(s):

Solar Cycle ◽

Resonance Frequency ◽

Fundamental Mode ◽

Lower Ionosphere ◽

Mode Frequency ◽

Schumann Resonance ◽

Schumann Resonances ◽

Cycle Minimum ◽

The North ◽

Cycle Maximum

A significant decrease of the fundamental Schumann resonance frequency during the solar cycle minimum of 2008-9 as observed at Modra ObservatoryThe Schumann resonances (SR) are electromagnetic eigenmodes of the resonator bounded by the Earth's surface and the lower ionosphere. The SR frequency variability has been studied for more than 4 decades. Using data from the period 1988 to 2002,Sátori et al. (2005)showed that the SR fundamental mode frequency decreased on the 11-year time scale by 0.07 - 0.2 Hz, depending on which component of the field was used for estimation and likely also on the location of the observer. A decrease by 0.30 Hz from the latest solar cycle maximum to the minimum of 2009 is found in data from Modra Observatory. This extraordinary fall of the fundamental mode frequency can be attributed to the unprecedented drop in the ionizing radiation in X-ray frequency band. Although the patterns of the daily and seasonal variations remain the same in the solar cycle minimum as in the solar cycle maximum, they are significantly shifted to lower frequencies during the minimum. Analysis of the daily frequency range suggests that the main thunderstorm regions during the north hemisphere summer are smaller in the solar cycle minimum than in the maximum.

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Prediction for the amplitude of solar cycle 24 from the pattern of activity near the cycle minimum

Kinematics and Physics of Celestial Bodies ◽

10.3103/s0884591313010054 ◽

2013 ◽

Vol 29 (1) ◽

pp. 37-43 ◽

Cited By ~ 1

Author(s):

M. I. Pishkalo

Keyword(s):

Solar Cycle ◽

Cycle Minimum ◽

Solar Cycle 24 ◽

Cycle 24

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Probability density functions for the variable solar wind near the solar cycle minimum

Journal of Geophysical Research Space Physics ◽

10.1002/2015ja021257 ◽

2015 ◽

Vol 120 (8) ◽

pp. 6152-6166 ◽

Cited By ~ 8

Author(s):

Z. Vörös ◽

M. Leitner ◽

Y. Narita ◽

G. Consolini ◽

P. Kovács ◽

...

Keyword(s):

Solar Wind ◽

Solar Cycle ◽

Probability Density ◽

Probability Density Functions ◽

Density Functions ◽

Cycle Minimum

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Active regions near the recent solar-cycle minimum: Relation between plasma heating and electrical currents

Astronomy Reports ◽

10.1134/s1063772913080027 ◽

2013 ◽

Vol 57 (8) ◽

pp. 611-621 ◽

Cited By ~ 4

Author(s):

I. Yu. Grigor’eva ◽

M. A. Livshits ◽

G. V. Rudenko ◽

I. I. Mysh’yakov

Keyword(s):

Solar Cycle ◽

Plasma Heating ◽

Active Regions ◽

Electrical Currents ◽

Cycle Minimum

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Extremely low geomagnetic activity during the recent deep solar cycle minimum

Proceedings of the International Astronomical Union ◽

10.1017/s174392131200484x ◽

2011 ◽

Vol 7 (S286) ◽

pp. 200-209 ◽

Cited By ~ 12

Author(s):

E. Echer ◽

B. T. Tsurutani ◽

W. D. Gonzalez

Keyword(s):

Solar Wind ◽

Solar Cycle ◽

Geomagnetic Activity ◽

Solar Minimum ◽

Solar Wind Speed ◽

Sunspot Cycle ◽

Cycle Minimum ◽

Current Minimum ◽

Solar Wind Parameters ◽

Xix Century

AbstractThe recent solar minimum (2008-2009) was extreme in several aspects: the sunspot number, Rz, interplanetary magnetic field (IMF) magnitude Bo and solar wind speed Vsw were the lowest during the space era. Furthermore, the variance of the IMF southward Bz component was low. As a consequence of these exceedingly low solar wind parameters, there was a minimum in the energy transfer from solar wind to the magnetosphere, and the geomagnetic activity ap index reached extremely low levels. The minimum in geomagnetic activity was delayed in relation to sunspot cycle minimum. We compare the solar wind and geomagnetic activity observed in this recent minimum with previous solar cycle values during the space era (1964-2010). Moreover, the geomagnetic activity conditions during the current minimum are compared with long term variability during the period of available geomagnetic observations. The extremely low geomagnetic activity observed in this solar minimum was previously recorded only at the end of XIX century and at the beginning of the XX century, and this might be related to the Gleissberg (80-100 years) solar cycle.

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