Statistical studies of geomagnetic storms with peak Dst≤−50nT from 1957 to 2008

Echer, E.; González, W. D.; Tsurutani, B. T.

doi:10.1016/j.jastp.2011.04.021

Cited by 72 publications

(79 citation statements)

References 47 publications

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“…One well-documented example is the occurrence frequency of geomagnetic storms, which has two peaks per year, at the equinoxes (e.g. Sabine, 1856;Cliver et al, 2000;Echer et al, 2011). This seasonal behaviour is often attributed to the Russell-McPherron mechanism (Russell and McPherron, 1973).…”

Section: Importance To Magnetospheric Dynamicsmentioning

confidence: 99%

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016

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Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90 • . The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

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Section: Importance To Magnetospheric Dynamicsmentioning

confidence: 99%

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016

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“…The SSNs of cycle 24 show two peaks: 98.3 in March 2012 and 116.4 in April 2014 (Svalgaard and Kamide 2013;Gopalswamy et al 2015). On a two-peak variation of geomagnetic activities seen in past solar cycles, Gonzalez et al (1990) and Echer et al (2011) noted that the first peak, appearing in the maximum phase, is caused by coronal mass ejections (CMEs) and the second peak, appearing in the declining phase, is caused by high-speed streams from coronal holes. Gopalswamy (2008) pointed out latitudinal distribution of CMEs had a close connection to the twopeak characteristics of geomagnetic activities.…”

Section: Introductionmentioning

confidence: 99%

“…There are numerous studies on geomagnetic storms and their solar sources in past cycles (Zhang et al 2007;Echer et al , 2011Richardson et al 2006;Richardson and Cane 2012a, b; references therein). According to the previous studies, the principal solar sources of intense geomagnetic storms (minimum Dst < −100 nT) were identified to be CMEs and approximately 11-14% of the storms were associated with high-speed streams from coronal holes (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Geomagnetic storms of cycle 24 and their solar sources

Watari¹

2017

Earth Planets Space

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Solar activity of cycle 24 following the deep minimum between cycle 23 and cycle 24 is the weakest one since cycle 14 (1902-1913). Geomagnetic activity is also low in cycle 24. We show that this low geomagnetic activity is caused by the weak dawn-to-dusk solar wind electric field (E d-d ) and that the occurrence rate of E d-d > 5 mV/m decreased in the interval from 2013 to 2014. We picked up seventeen geomagnetic storms with the minimum Dst index of less than −100 nT and identified their solar sources in cycle 24 (2009-2015). It is shown that the relatively slow coronal mass ejections contributed to the geomagnetic storms in cycle 24.

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“…In comparison, only a few studies have been performed on moderate (À50 nT ≤ Dst < À100 nT) storms [Tsurutani and Gonzalez, 1997;Wang et al, 2003;Zhang et al, 2006;Xu et al, 2009;Echer et al, 2011;Hutchinson et al, 2011;Tsurutani et al, 2011a]. None of the previous studies were done over an entire solar cycle.…”

Section: Introductionmentioning

confidence: 99%

Interplanetary origins of moderate (−100 nT < Dst ≤ −50 nT) geomagnetic storms during solar cycle 23 (1996–2008)

2013

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[1] The interplanetary causes of 213 moderate-intensity (À100 nT < peak Dst ≤ À50 nT) geomagnetic storms that occurred in solar cycle 23 (1996-2008) are identified.Interplanetary drivers such as corotating interaction regions (CIRs), pure high-speed streams (HSSs), interplanetary coronal mass ejections (ICMEs) of two types [those with magnetic clouds (MCs) and those without (nonmagnetic cloud or ICME_nc)], sheaths (compressed and/or draped sheath fields), as well as their combined occurrence were identified as causes of the storms. The annual rate of occurrence of moderate storms had two peaks, one near solar maximum and the other in the descending phase, around 3 years later. The highest rate of moderate storm occurrence was found in the declining phase (25 storms year À1 ). The lowest occurrence rate was 5.7 storms year À1 and occurred at solar minimum. All moderate-intensity storms were associated with southward interplanetary magnetic fields, indicating that magnetic reconnection was the main mechanism for solar wind energy transfer to the magnetosphere. Most of these storms were associated with CIRs and pure HSSs (47.9%), followed by MCs and noncloud ICMEs (20.6%), pure sheath fields (10.8%), and sheath and ICME combined occurrence (9.9%). In terms of solar cycle dependence, CIRs and HSSs are the dominant drivers in the declining phase and at solar minimum. CIRs and HSSs combined have about the same level of importance as ICMEs plus their sheaths in the rising and maximum solar cycle phases. Thus, CIRs and HSSs are the main driver of moderate storms throughout a solar cycle but with variable contributions from ICMEs, their shocks (sheaths), and combined occurrence within the solar cycle. This result is significantly different than that for intense (Dst ≤ À100 nT) and superintense (Dst ≤ À250 nT) magnetic storms shown in previous studies. For superintense geomagnetic storms, 100% of the events were due to ICME events, while for intense storms, ICMEs, sheaths, and their combination caused almost 80% of the storms. CIRs caused only 13% of the intense storms. The typical interplanetary electric field (Ey) criteria for moderate magnetic storms were identified. It was found that~80.1% of the storms follow the criterion of Ey ≥ 2 mV m À1 for intervals longer than 2 h. It is concluded that southward directed interplanetary magnetic fields within CIRs/HSSs may be the main energy source for long-term averaged geomagnetic activity on Earth.

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Statistical studies of geomagnetic storms with peak Dst≤−50nT from 1957 to 2008

Cited by 72 publications

References 47 publications

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

Geomagnetic storms of cycle 24 and their solar sources

Interplanetary origins of moderate (−100 nT < Dst ≤ −50 nT) geomagnetic storms during solar cycle 23 (1996–2008)

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