Deep Solar Activity Minimum 2007 – 2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

Farrugia, C. J.; Harris, B.; Leitner, M.; Möstl, Christian; Galvin, A. B.; Simunac, K. D. C.; Torbert, R. B.; Temmer, Manuela; Veronig, Astrid; Еркаев, Н. В.; Szabó, Á.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V. A.

doi:10.1007/s11207-012-0119-1

Cited by 7 publications

(8 citation statements)

References 52 publications

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“…The ST frequency peaks in the minimum years 2007–2009 and reaches a clear maximum in 2009 at the depth of the unusual and prolonged solar minimum of cycle 24 [e.g., Farrugia et al , , and references therein]. Note that year 2009 is not only at solar minimum but is also a year where the incidence of slow wind was the highest in the period (92%, 89%, and 90% at STB, Wind, and STA, respectively).…”

Section: Resultsmentioning

confidence: 99%

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Farrugia

Galvin

et al. 2016

JGR Space Physics

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This paper discusses small solar wind transients (STs) from 1995 to 2014. Using STEREO data, we have more sites from which to study STs near 1 AU. STEREO measurements are compared with wind observations near the Sun‐Earth line. We examined statistically the dependence of ST occurrence frequency on (i) solar cycle phase, as monitored by the sunspot number (SSN), and (ii) solar wind speed. We find dependencies on both: an anticorrelation with SSN, an opposite trend to that of interplanetary coronal mass ejections (ICMEs), and correlation with slow solar wind (over 80% in the slow wind). We compare ST distributions during solar maximum year 2003, which had the lowest percentage of slow wind, and minimum year 2009, which had the highest percentage thereof, and show evidence of both dependencies. We give a statistical overview of ST parameters: field strength, B, Alfvén Mach number, MA, and proton beta, βp. They show the same temporal trends as the ambient solar wind but have twice (B) or one half (MA, βp) of its average values. In STs, the proton temperature is not below the temperature expected from corotating solar wind expansion. Non‐force free models should be used in solar minimum years where βplasma≈ 1, while the force free models could be used in solar maximum when βplasma<<1. We find that only ∼5% of STs show enhanced values of iron charge states. Our work further supports the two‐source origin of STs, i.e., the solar corona and the interplanetary medium.

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Section: Resultsmentioning

confidence: 99%

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Farrugia

Galvin

et al. 2016

JGR Space Physics

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“…[], and the approximation of Fairfield and models by Sibeck et al'91 and Shue et al'97 were used by Farrugia et al . [], the models by Fairfield and Shue et al'97 were used by Turner et al . [].…”

Section: Models and Magnetopause Standoff Distance Approximationsmentioning

confidence: 99%

Magnetopause inflation under radial IMF: Comparison of models

Suvorova

Дмитриев

2015

Earth and Space Science

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The solar wind with the radial interplanetary magnetic field (IMF) flowing around the Earth's magnetosphere can result in significant decrease of a total pressure in the magnetosheath that was directly observed by Time History of Events and Macroscale Interactions during Substorms satellites. Observations also showed that the dayside magnetosphere enlarged and the magnetopause inflated far away from the Earth that differs from the classical hydrodynamic case. Full understanding of the magnetosphere interaction with such "radial" flow, is far from completeness. One of the reasons is a quantitative uncertainty in description of this effect. We have performed a comparative analysis of 14 magnetopause models in order to estimate their prediction capabilities under various solar wind pressures and in particular under very low pressures during the time intervals of quasi-radial IMF orientation. We have found that only 4 out of 14 models allow predicting the magnetopause under extremely low pressures and, hence, can be useful for quantitative estimation of the magnetopause expansion under quasi-radial IMF orientation. Those models are characterized by relatively large power index α in the pressure balance; that is, α = 1/5.2 ≈ 0.192 for 3 out of 4 models.

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“…Many papers have found variables of near‐Earth interplanetary space and the magnetosphere approximately follow a lognormal (or similar) distribution for the great majority of the time (Dmitriev et al, ; Farrugia et al, ; Hapgood et al, ; Lockwood & Wild, ; Lotz & Danskin, ; Love et al, ; Riley & Love, ; Vaselovsky et al, ; Vörös et al, ; Weigel & Baker, ; Xiang & Qu, ). This mathematical formulation describes the core of the distribution but often fails to match the occurrence of very large or extreme events (e.g., Baker et al, ; Cliver & Dietrich, ; Lotz & Danskin, ; Riley, ).…”

Section: Introductionmentioning

confidence: 99%

The Development of a Space Climatology: 3. Models of the Evolution of Distributions of Space Weather Variables With Timescale

et al. 2019

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We study how the probability distribution functions of power input to the magnetosphere P α and of the geomagnetic ap and Dst indices vary with averaging timescale, τ, between 3 hr and 1 year. From this we develop and present algorithms to empirically model the distributions for a given τ and a given annual mean value. We show that lognormal distributions work well for ap, but because of the spread of Dst for low activity conditions, the optimum formulation for Dst leads to distributions better described by something like the Weibull formulation. Annual means can be estimated using telescope observations of sunspots and modeling, and so this allows the distributions to be estimated at any given τ between 3 hr and 1 year for any of the past 400 years, which is another important step toward a useful space weather climatology. The algorithms apply to the core of the distributions and can be used to predict the occurrence rate of large events (in the top 5% of activity levels): they may contain some, albeit limited, information relevant to characterizing the much rarer superstorm events with extreme value statistics. The algorithm for the Dst index is the more complex one because, unlike ap, Dst can take on either sign and future improvements to it are suggested.Plain Language Summary This is the third in a series of three papers aimed at developing a climatology of space weather that applies to all solar conditions between grand solar minimum and grand solar maximum. We generate empirical models to enable us to predict the probability of a given level of space weather disturbance, as quantified by either the ap of the Dst geomagnetic indices, in a year with a given average level of disturbance. The models can be used with averaging/integration times anywhere between 3 hr and 1 year. , et al. (2019). The development of a space climatology: 3. Models of the evolution of distributions of space weather variables with timescale. Space Weather, 17, 180-209. https://doi.

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Deep Solar Activity Minimum 2007 – 2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

Cited by 7 publications

References 52 publications

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Magnetopause inflation under radial IMF: Comparison of models

The Development of a Space Climatology: 3. Models of the Evolution of Distributions of Space Weather Variables With Timescale

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