scholarly journals The Two‐Dimensional Evolution of Thermospheric ∑O/N 2 Response to Weak Geomagnetic Activity During Solar‐Minimum Observed by GOLD

2020 ◽  
Vol 47 (18) ◽  
Author(s):  
Xuguang Cai ◽  
Alan G. Burns ◽  
Wenbin Wang ◽  
Liying Qian ◽  
Stanley C. Solomon ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Two Dimensional

Intermediate Layers responses to Geomagnetic Activity During the 2009 Deep Solar Minimum Over the Brazilian Low Latitude Sector

2021 ◽  
Author(s):  
Angela M Santos ◽  
C G M Brum ◽  
I S Batista ◽  
J H A Sobral ◽  
M A Abdu ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Low Latitude ◽  
Intermediate Layers

scholarly journals Spectral analysis of auroral geomagnetic activity during various solar cycles between 1960 and 2014

2016 ◽  
Vol 34 (12) ◽  
pp. 1159-1164 ◽  
Author(s):  
Pieter Benjamin Kotzé
Keyword(s):  
Spectral Analysis ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
High Speed ◽  
Solar Rotation ◽  
Pearson Correlation ◽  
Coronal Holes ◽  
Rotation Period ◽  
Period Change ◽  
Solar Cycles

Abstract. In this paper we use wavelets and Lomb–Scargle spectral analysis techniques to investigate the changing pattern of the different harmonics of the 27-day solar rotation period of the AE (auroral electrojet) index during various phases of different solar cycles between 1960 and 2014. Previous investigations have revealed that the solar minimum of cycles 23–24 exhibited strong 13.5- and 9.0-day recurrence in geomagnetic data in comparison to the usual dominant 27.0-day synodic solar rotation period. Daily mean AE indices are utilized to show how several harmonics of the 27-day recurrent period change during every solar cycle subject to a 95 % confidence rule by performing a wavelet analysis of each individual year's AE indices. Results show that particularly during the solar minimum of 23–24 during 2008 the 27-day period is no longer detectable above the 95 % confidence level. During this interval geomagnetic activity is now dominated by the second (13.5-day) and third (9.0-day) harmonics. A Pearson correlation analysis between AE and various spherical harmonic coefficients describing the solar magnetic field during each Carrington rotation period confirms that the solar dynamo has been dominated by an unusual combination of sectorial harmonic structure during 23–24, which can be responsible for the observed anomalously low solar activity. These findings clearly show that, during the unusual low-activity interval of 2008, auroral geomagnetic activity was predominantly driven by high-speed solar wind streams originating from multiple low-latitude coronal holes distributed at regular solar longitude intervals.

scholarly journals Extremely low geomagnetic activity during the recent deep solar cycle minimum

2011 ◽  
Vol 7 (S286) ◽  
pp. 200-209 ◽  
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.

scholarly journals Investigating the foF2 variations at the Ionospheric Observatory of Rome during different solar cycles minimums and levels of geomagnetic activity

2020 ◽  
Vol 10 ◽  
pp. 52
Author(s):  
Alessandro Ippolito ◽  
Loredana Perrone ◽  
Christina Plainaki ◽  
Claudio Cesaroni
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Critical Frequency ◽  
Background Level ◽  
Solar Cycles ◽  
Physical Processes ◽  
Minimum Duration ◽  
Critical Frequency Fof2 ◽  
Definition Of ◽  
Low Activity

The variations of the hourly observations of the critical frequency foF2, recorded at the Ionospheric Observatory of Rome by the AIS-INGV ionosonde (geographic coordinates 41.82° N, 12.51° E; geomagnetic coordinates 41.69° N, 93.97° E) during the low activity periods at the turn of solar cycles 21–22, 22–23 and 23–24, are investigated. Deviations of foF2 greater than ± 15% with respect to a background level, and with a minimum duration of 3 h, are here considered anomalous. The dependence of these foF2 anomalies on geomagnetic activity has been accurately investigated. Particular attention has been paid to the last deep solar minimum 2007–2009, in comparison with the previous solar cycle minima. The lack of day-time anomalous negative variations in the critical frequency of the F2 layer, is one of the main findings of this work. Moreover, the analysis of the observed foF2 anomalies confirms the existence of two types of positive F2 layer disturbances, characterised by different morphologies and, different underlying physical processes. A detailed analysis of four specific cases allows the definition of possible scenarios for the explanation of the mechanisms behind the generation of the foF2 anomalies.

scholarly journals An alternative way to identify local geomagnetically quiet days: a case study using wavelet analysis

2016 ◽  
Vol 34 (4) ◽  
pp. 451-462 ◽  
Author(s):  
Virginia Klausner ◽  
Andrés Reinaldo Rodriguez Papa ◽  
Cláudia Maria Nicole Cândido ◽  
Margarete Oliveira Domingues ◽  
Odim Mendes
Keyword(s):  
Wavelet Analysis ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
High Speed ◽  
Wavelet Coefficient ◽  
Magnetic Activity ◽  
New Method ◽  
Storm Events ◽  
High Speed Stream

Abstract. This paper proposes a new method to evaluate geomagnetic activity based on wavelet analysis during the solar minimum activity (2007). In order to accomplish this task, a newly developed algorithm called effectiveness wavelet coefficient (EWC) was applied. Furthermore, a comparison between the 5 geomagnetically quiet days determined by the Kp-based method and by wavelet-based method was performed. This paper provides a new insight since the geomagnetic activity indexes are mostly designed to quantify the extent of disturbance rather than the quietness. The results suggest that the EWC can be used as an alternative tool to accurately detect quiet days, and consequently, it can also be used as an alternative to determine the Sq baseline to the current Kp-based 5 quietest days method. Another important aspect of this paper is that most of the quietest local wavelet candidate days occurred in an interval 2 days prior to the high-speed-stream-driven storm events. In other words, the EWC algorithm may potentially be used to detect the quietest magnetic activity that tends to occur just before the arrival of high-speed-stream-driven storms.

scholarly journals Dayside ionospheric response to recurrent geomagnetic activity during the extreme solar minimum of 2008

2010 ◽  
Vol 37 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
S. Tulasi Ram ◽  
J. Lei ◽  
S.-Y. Su ◽  
C. H. Liu ◽  
C. H. Lin ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Ionospheric Response

scholarly journals Intermediate Layers responses to Geomagnetic Activity During the 2009 Deep Solar Minimum Over the Brazilian Low Latitude Sector

2021 ◽  
Author(s):  
Ângela Santos ◽  
Christiano Brum ◽  
Inez Batista ◽  
José Sobral ◽  
Mangalathayil Abdu ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Early Morning ◽  
Low Latitude ◽  
Seasonal Behavior ◽  
F Region ◽  
Intermediate Layers ◽  
Bottom Side ◽  
E Region ◽  
First Time

Abstract. Intermediate layers (ILs) are regions of enhanced electron density located in the ionospheric valley that extends from the peak altitude of the daytime E-region to the bottom side of the F-region. This work presents the daytime behavior of the ILs parameters (the virtual height - h’IL, and the top frequency - ftIL) over the low latitude region of Cachoeria Paulista (CP, 22.42° S; 45° W, I: −34.4°) for the deepest solar minimum of the last 500 years. In such a unique condition, this research reveals for the first time the ILs' quiet state seasonal behavior as well as its responses to moderate changes in the geomagnetic activity. The main results show that even small variations of geomagnetic activity (quantified by the planetary Kp index) are able to modify the dynamics of the ILs parameters. For the first time, it was observed that during the summer, the h’IL decrease rapidly with the increase of geomagnetic activity mainly in the early morning hours. In the following hours, a smoothed rise of the IL was found in all seasons analyzed. Regarding to frequency, it was observed that after 12:00 LT, there is a tendency of it decreased with the increase of the magnetic disturbances, being this characteristic more intense after 16:00 LT, except in the equinox, when little or no response was found during all the interval analyzed. In addition, it stands out that the annual periodicity of the ftIL was observed while the h’IL presents semiannual component.

scholarly journals Geomagnetic activity effect on the global ionosphere during the 2007-2009 deep solar minimum

2014 ◽  
Vol 119 (5) ◽  
pp. 3747-3754 ◽  
Author(s):  
Yiding Chen ◽  
Libo Liu ◽  
Huijun Le ◽  
Weixing Wan
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Activity Effect
Sign in / Sign up

Export Citation Format

Share Document