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Register a new userCandidate Auroral Observations during the Major Solar-Terrestrial Storm in May 1680: Implication for Space Weather Events during the Maunder Minimum
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The Maunder Minimum (1645-1715) is currently considered the only grand minimum within telescopic sunspot observations since 1610. During this epoch, the Sun was extremely quiet and unusually free from sunspots. However, despite reduced frequency, candidate aurorae were reported in the mid-European sector during this period and have been associated with occurrences of interplanetary coronal mass ejections (ICMEs), whereas some of them have been identified as misinterpretations. Here, we have analysed reports of candidate aurorae on 1 June 1680 with simultaneous observations in mid-Europe, and compared their descriptions with visual accounts of early modern aurorae. Most contemporary sunspot drawings from 22, 24, and 27 May 1680 have shown that this apparent sunspot may have been a source of ICMEs, which caused the reported candidate aurorae. On the other hand, its intensity estimate shows that the magnetic storm during this candidate aurora was probably within the capability of the storms derived from the corotating interaction region (CIR). Therefore, we accommodate both ICMEs and CIRs as their possible origin. This interpretation is probably applicable to the candidate aurorae in the often-cited Hungarian catalogue, on the basis of the reconstructed margin of their equatorward auroral boundary. Moreover, this catalogue itself has clarified that the considerable candidates during the MM were probably misinterpretations. Therefore, frequency of the auroral visibility in Hungary was probably lower than previously considered and agree more with the generally slow solar wind in the existing reconstructions, whereas sporadic occurrences of sunspots and coronal holes still caused occasional geomagnetic storms.
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The importance of the investigation of magnetic superstorms is not limited to academic interest, because these superstorms can cause catastrophic impact on the modern civilisation due to our increasing dependency on technological infrastructure. In this context, the Carrington storm in September 1859 is considered as a benchmark of observational history owing to its magnetic disturbance and equatorial extent of the auroral oval. So far, several recent auroral reports at that time have been published but those reports are mainly derived from the Northern Hemisphere. In this study, we analyse datable auroral reports from South America and its vicinity, assess the auroral extent using philological and astrometric approaches, identify the auroral visibility at - 17.3{deg} magnetic latitude and further poleward and reconstruct the equatorial boundary of the auroral oval to be 25.1{deg} +/- 0.5{deg} in invariant latitude. Interestingly, brighter and more colourful auroral displays were reported in the South American sector than in the Northern Hemisphere. This north-south asymmetry is presumably associated with variations of their magnetic longitude and the weaker magnetic field over South America compared to the magnetic conjugate point and the increased amount of magnetospheric electron precipitation into the upper atmosphere. These results attest that the magnitude of the Carrington storm indicates that its extent falls within the range of other superstorms, such as those that occurred in May 1921 and February 1872, in terms of the equatorial boundary of the auroral oval.
The sun occasionally undergoes the so-called grand minima, in which its magnetic activity, measured by the number of sunspots, is suppressed for decades. The most prominent grand minima, since the beginning of telescopic observations of sunspots, is the Maunder minimum (1645-1715), when the sunspots became rather scarce. The mechanism underlying the grand minima remains poorly understood as there is little observational information of the solar magnetic field at that time. In this study, we examine the records of one candidate aurora display in China and Japan during the Maunder minimum. The presence of auroras in such mid magnetic latitudes indicates the occurrence of great geomagnetic storms that are usually produced by strong solar flares. However, the records of contemporary sunspot observations from Europe suggest that, at least for the likely aurora event, there was no large sunspot that could produce a strong flare. Through simple theoretical arguments, we show that this geomagnetic storm could have been generated by an eruption giant quiescent filament, or a series of such events.
In addition to the regular Schwabe cycles of approximately 11 y, prolonged solar activity minima have been identified through the direct observation of sunspots and aurorae, as well as proxy data of cosmogenic isotopes. Some of these minima have been regarded as grand solar minima, which are arguably associated with the special state of the solar dynamo and have attracted significant scientific interest. In this paper, we review how these prolonged solar activity minima have been identified. In particular, we focus on the Dalton Minimum, which is named after John Dalton. We review Daltons scientific achievements, particularly in geophysics. Special emphasis is placed on his lifelong observations of auroral displays over approximately five decades in Great Britain. Daltons observations for the auroral frequency allowed him to notice the scarcity of auroral displays in the early 19th century. We analyze temporal variations in the annual frequency of such displays from a modern perspective. The contemporary geomagnetic positions of Daltons observational site make his dataset extremely valuable because his site is located in the sub-auroral zone and is relatively sensitive to minor enhancements in solar eruptions and solar wind streams. His data indicate clear solar cycles in the early 19th century and their significant depression from 1798 to 1824. Additionally, his data reveal a significant spike in auroral frequency in 1797, which chronologically coincides with the lost cycle that is believed to have occurred at the end of Solar Cycle 4. Therefore, John Daltons achievements can still benefit modern science and help us improve our understanding of the Dalton Minimum.
We study the interaction of three solar wind structures, two stream interaction regions and one interplanetary coronal mass ejection, with Mars plasma environment during 20-27 November 2007. This period corresponds to the solar minimum between the solar cycles 23 and 24 which was characterized by very low values of the solar wind density and dynamic pressure and low IMF magnitude. During that time the Mars-Express orbit was in the terminator plane, while the Earth, Sun, and Mars were almost aligned, so we use the ACE and STEREO probes as solar wind monitors in order to identify and characterize the structures that later hit Mars. We find that the passage of these structures caused strong variations of in the bow shock location (between 2.2 and 3.0~R$_M$), compression of the magnetospheric cavity (up to 45~%) and an increased transterminator flow below 2~R$_M$ (by a factor of $leq$8). This study shows that during times of low solar activity, modest space weather phenomena may cause large variations of plasma flow at Mars.
textit{Parker Solar Probe} has shown the ubiquitous presence of strong magnetic field deflections, namely switchbacks, during its first perihelion where it was embedded in a highly Alfvenic slow stream. Here, we study the turbulent magnetic fluctuations around ion scales in three intervals characterized by a different switchback activity, identified by the behaviour of the magnetic field radial component, $B_r$. textit{Quiet} ($B_r$ does not show significant fluctuations), textit{weak} ($B_r$ has strong fluctuations but no reversals) and textit{strong} ($B_r$ has full reversals) periods show a different behaviour also for ion quantities and Alfvenicity. However, the spectral analysis shows that each stream is characterized by the typical Kolmogorov/Kraichnan power law in the inertial range, followed by a break around the characteristic ion scales. This frequency range is characterized by strong intermittent activity, with the presence of non-compressive coherent structures, such as current sheets and vortex-like structures, and wave packets, identified as ion cyclotron modes. Although, all these intermittent events have been detected in the three periods, they have a different influence in each of them. Current sheets are dominant in the textit{strong} period, wave packets are the most common in the textit{quiet} interval; while, in the textit{weak} period, a mixture of vortices and wave packets is observed. This work provides an insight into the heating problem in collisionless plasmas, fitting in the context of the new solar missions, and, especially for textit{Solar Orbiter}, which will allow an accurate magnetic connectivity analysis, to link the presence of different intermittent events to the source region.
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