Galactic cosmic ray radiation hazard in the unusual extended solar minimum between solar cycles 23 and 24

Schwadron, N. A.; Boyd, A. J.; Kozarev, Kamen; Golightly, M. J.; Townsend, L. W.; Owens, M. J.

doi:10.1029/2010sw000567

Cited by 36 publications

(32 citation statements)

References 35 publications

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“…The GCR intensity modulation in the minimum 23/24 is also a broadly investigated subject because of its very unusual character (e.g., Heber et al, 2009;McDonald, Webber, and Reames, 2010;Schwadron et al, 2010). Recently, Paouris et al (2012) studied the GCR modulation in the minimum 23/24 in relation to solar activity indices and heliospheric parameters, such as the sunspot number, the interplanetary magnetic field, the CME index, and the tilt angle of the heliospheric current sheet.…”

Section: Introductionmentioning

confidence: 99%

The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24

Modzelewska

Alania

2013

Sol Phys

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We have studied the 27-day variations and their harmonics in Galactic cosmic ray (GCR) intensity, solar wind velocity, and interplanetary magnetic field (IMF) components during the recent prolonged solar minimum 23/24. The time evolution of the quasiperiodicity in these parameters connected with the Sun's rotation reveals that the synodic period of these variations is ≈ 26 -27 days and is stable. This means that the changes in the solar wind speed and the IMF are related to the Sun's near-equatorial regions in considering the differential rotation of the Sun. However, the solar wind parameters observed near the Earth's orbit provide only the conditions in the limited local vicinity of the equatorial region in the heliosphere (within ± 7• in latitude). We also demonstrate that the observed period of the GCR intensity connected with the Sun's rotation increased up to ≈ 33 -36 days in 2009. This means that the process that drives the 27-day GCR intensity variations takes place not only in the limited local surroundings of the equatorial region but in the global 3-D space of the heliosphere, covering also higher latitude regions. A relatively long period (≈ 34 days) found for 2009 in the GCR intensity gives possible evidence of the onset of cycle 24 due to active regions at higher latitudes and rotating slowly because of the Sun's differential rotation. We also discuss the effect of differential rotation on the theoretical model of the 27-day GCR intensity variations.

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Section: Introductionmentioning

confidence: 99%

The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24

Modzelewska

Alania

2013

Sol Phys

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“…4) may indicate that an inhibiting effect on the prediction outcome due to complex interplanetary conditions between the Sun and Earth is indeed real. It is noted that the decay phase of solar cycle 23 was characterized by an unusual period of reduced solar activity and low interplanetary magnetic field strengths (Schwadron et al, 2010). Also, these authors reported that the extended solar minimum of 2009-2010, which extended between solar cycles 23 and 24, was marked by fluxes of galactic cosmic ray radiation at near to their highest level in 25 years.…”

Section: Possible Influence On the Predictions Of The Phase Of The Somentioning

confidence: 87%

A statistical study of the performance of the Hakamada-Akasofu-Fry version 2 numerical model in predicting solar shock arrival times at Earth during different phases of solar cycle 23

McKenna‐Lawlor

Fry²,

Dryer³

et al. 2012

Ann. Geophys.

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Abstract. The performance of the Hakamada Akasofu-Fry, version 2 (HAFv.2) numerical model, which provides predictions of solar shock arrival times at Earth, was subjected to a statistical study to investigate those solar/interplanetary circumstances under which the model performed well/poorly during key phases (rise/maximum/decay) of solar cycle 23. In addition to analyzing elements of the overall data set (584 selected events) associated with particular cycle phases, subsets were formed such that those events making up a particular sub-set showed common characteristics. The statistical significance of the results obtained using the various sets/subsets was generally very low and these results were not significant as compared with the hit by chance rate (50 %). This implies a low level of confidence in the predictions of the model with no compelling result encouraging its use. However, the data suggested that the success rates of HAFv.2 were higher when the background solar wind speed at the time of shock initiation was relatively fast. Thus, in scenarios where the background solar wind speed is elevated and the calculated success rate significantly exceeds the rate by chance, the forecasts could provide potential value to the customer. With the composite statistics available for solar cycle 23, the calculated success rate at high solar wind speed, although clearly above 50 %, was indicative rather than conclusive. The RMS error estimated for shock arrival times for every cycle phase and for the composite sample was in each case significantly better than would be expected for a random data set. Also, the parameter "Probability of Detection, yes" (PODy) which presents the Proportion of Yes observations that were correctly forecast (i.e. the ratio between the shocks correctly predicted and all the shocks observed), yielded values for the rise/maximum/decay phases of the cycle and using the composite sample of 0.85, 0.64, 0.79 and 0.77, respectively. The statistical results obtained through detailed analysis of the available data provided insights into how changing circumstances on the Sun and in interplanetary space can affect the performance of the model. Since shock arrival predictions are widely utilized in making commercially significant decisions re. protecting space assets, the present detailed archival studies can be useful in future operational decision making during solar cycle 24. It would be of added value in this context to use Briggs-Rupert methodology to estimate the cost to an operator of acting on an incorrect forecast.

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“…These parameters affected other heliospheric conditions including the galactic cosmic ray flux (e.g. Schwadron et al 2010). The altered solar wind dynamic pressure also had significant impacts on planetary plasma interactions and geomagnetic activity.…”

Section: Introductionmentioning

confidence: 99%

Interplanetary conditions: lessons from this minimum

et al. 2011

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Abstract.Interplanetary conditions during the Cycle 23-24 minimum have attracted attention because they are noticeably different than those during other minima of the space age, exhibiting more solar wind stream interaction structures in addition to reduced mass fluxes and low magnetic field strengths. In this study we consider the differences in the solar wind source regions by applying Potential Field Source Surface models of the coronal magnetic field. In particular, we consider the large scale coronal field geometry that organizes the open field region locations and sizes, and the appearance of the helmet streamer structure that is another determiner of solar wind properties. The recent cycle minimum had an extraordinarily long entry phase (the decline of Cycle 23) that made it difficult to identify when the actual miminum arrived. In particular, the late 23 r d cycle was characterized by diminishing photospheric fields and complex coronal structures that took several extra years to simplify to its traditional dipolar solar minimum state. The nearly dipolar phase, when it arrived, had a duration somewhat shorter than those of the previous cycles. The fact that the corona maintained an appearance more like a solar maximum corona through most of the quiet transitional phase between Cycles 23 and 24 gave the impression of a much more complicated solar minimum solar wind structure in spite of the weaknesses of the mass flux and interplanetary field. The extent to which the Cycle 23-24 transition will affect Cycle 24, and/or represents what happens during weak cycles in general, remains to be seen.

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Galactic cosmic ray radiation hazard in the unusual extended solar minimum between solar cycles 23 and 24

Cited by 36 publications

References 35 publications

The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24

The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24

A statistical study of the performance of the Hakamada-Akasofu-Fry version 2 numerical model in predicting solar shock arrival times at Earth during different phases of solar cycle 23

Interplanetary conditions: lessons from this minimum

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