Sunspot activity and cosmic ray modulation at 1 a.u. for 1900–2013

The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006–2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (μT) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u.     

He-like Ar xvii triplet observed by RESIK

We present the observations of He-like Ar triplet lines obtained by RESIK spectrometer aboard CORONAS-F. Interpretation of intensity ratios between triplet lines of lower Z elements is known to provide useful diagnostics of plasma conditions within the emitting source. Here, we investigate whether triplet line ratios are useful for interpretation of higher Z element spectra. A high sensitivity, low background and precise absolute calibration of RESIK allow to consider in addition also the continuum contribution. This provides a way to determine the Ar absolute abundance from the observed triplet component ratios. The method is presented and the results are shown for two selected flares. Derived values of Ar absolute abundance for these flares are found to be similar: 2.6 × 10⁻⁶ and 2.9 × 10⁻⁶. They fall in the range between presently accepted Ar photospheric and coronal abundances.     

A broad climatology of very high latitude substorms

Magnetic data from a newly commissioned Indian Antarctic station Bharati (corrected geomagnetic (CGM) coordinates 74.7°S, 97.2°E) and closely-spaced IMAGE chain observatories (∼100° magnetic meridian in Northern hemisphere) has been analyzed to study the climatology of substorms which were localized poleward of the standard auroral oval. We considered four austral summers (year 2007–2010) when data from Bharati was available. Several very high latitude substorms were observed in this duration when the solar activity remained unexpectedly low for a long time. Various features of very high latitude substorms, e.g., local time dependence, interplanetary state, hemispherical asymmetry and their nightside low latitude signatures are examined. Events studied here, suggested the following properties of substorms occurring at very high latitudes: (1) maximum occurrence was observed near magnetic midnight (21:00–02:00 MLT). (2) In contradiction to earlier reports, many substorms were observed even during negative IMF Bz condition. In addition, majority of substorms occurred during low or moderate solar wind streams. (3) Magnetic signatures were often pronounced in the winter hemisphere. (4) Even if widely used standard AE indices fail to monitor very high latitude substorms, their low latitude signatures are often evident.     

Survival and death of the haloarchaeon Natronorubrum strain HG-1 in a simulated martian environment

Halophilic archaea are of interest to astrobiology due to their survival capabilities in desiccated and high salt environments. The detection of remnants of salty pools on Mars stimulated investigations into the response of haloarchaea to martian conditions. Natronorubrum sp. strain HG-1 is an extremely halophilic archaeon with unusual metabolic pathways, growing on acetate and stimulated by tetrathionate. We exposed Natronorubrum strain HG-1 to ultraviolet (UV) radiation, similar to levels currently prevalent on Mars. In addition, the effects of low temperature (4, −20, and −80 °C), desiccation, and exposure to a Mars soil analogue from the Atacama desert on the viability of Natronorubrum strain HG-1 cultures were investigated. The results show that Natronorubrum strain HG-1 cannot survive for more than several hours when exposed to UV radiation equivalent to that at the martian equator. Even when protected from UV radiation, viability is impaired by a combination of desiccation and low temperature. Desiccating Natronorubrum strain HG-1 cells when mixed with a Mars soil analogue impaired growth of the culture to below the detection limit. Overall, we conclude that Natronorubrum strain HG-1 cannot survive the environment currently present on Mars. Since other halophilic microorganisms were reported to survive simulated martian conditions, our results imply that survival capabilities are not necessarily shared between phylogenetically related species.     

The hydroxyl radical as an indicator of SEP fluxes in the high-latitude terrestrial atmosphere

The low background values at nighttime of the mesospheric hydroxyl (OH) radical make it easier to single out the atmospheric response to the external solar forcing in Polar Regions. Because of the short lifetime of HO_x, it is possible to follow the trails of Solar Energetic Particle (SEP) events in the terrestrial atmosphere, as shown by Storini and Damiani (2008). The sensitivity of this indicator makes discernible not only extreme particle events with a flux peak of several thousand pfu [1 pfu = 1 particle/(cm² s sr)] at energies >10 MeV, but also those with lower flux up to about 300 pfu. Using data from the Microwave Limb Sounder (MLS) on board the EOS AURA satellite, we examined the correlation of OH abundance vs. solar proton flux for almost all the identified SEP events spanning from November 2004 to December 2006 (later on no more SEP events occurred during Solar Cycle no. 23). The channels at energies greater than 5 MeV and 10 MeV showed the best correlation values (r ∼ 0.90–0.95) at altitudes around 65–75 km whereas, as expected, the most energetic channels were most highly correlated at lower altitudes. Therefore, it is reasonably possible to estimate the solar proton flux from values of mesospheric OH (and viceversa) and it could be useful in studying periods with gaps in the records of solar particles.     

A calibration neutron monitor: Statistical accuracy and environmental sensitivity

This paper is a follow-on of that of Krüger et al. [Krüger, H., Moraal, H., Bieber, J.W., Clem, J.M., Evenson, P.A., Pyle, K.R., Duldig, M.L., Humble, J.E. A calibration neutron monitor: energy response and instrumental temperature sensitivity. J. Geophys. Res. 113, A08101, doi:10.1029/2008JA013229, 2008], that describes the characteristics of a pair of calibration neutron monitors that were developed to intercalibrate the count rates of the world’s neutron monitors against each other. Such an intercalibration will allow the calculation of energy (rigidity) spectra, which will enhance the quality of the neutron monitor data. Krüger et al. (2008) investigated the energy and temperature response of the calibrators. This paper studies the statistical accuracy of the calibration procedure, its repeatability, and the sensitivity to its environment. The paper concludes with a calibration procedure that can minimise the uncertainties caused by these five effects, or at least correct for them.     

The origin of the prompt optical emission in GRB 060111B

The detection of a bright optical emission measured with good temporal resolution during the prompt phase makes GRB 060111B a rare event that is especially useful for constraining theories of the prompt optical emission. Comparing this burst with other GRBs with evidence of optical peaks, we find that the optical peak epoch (t_p) is anti-correlated with the high energy burst energetic assuming an isotropic energy release (E_iso) in agreement with Liang et al. (2009), and that the steeper is the post-peak afterglow decay, the less is the agreement with the correlation. GRB 060111B is among the latters and it does not match the correlation. The Cannonball scenario is also discussed and we find that this model cannot be excluded for GRB 060111B.     

Science operations planning expertise: A neglected component of mission design

In this paper, Science Operations Planning Expertise (SOPE) is defined as the expertise that is held by people who have the two following qualities. First they have both theoretical and practical experience in operations planning, in general, and in space science operations planning in particular. Second, they can be used, on request and at least, to provide with advice the teams that design and implement science operations systems in order to optimise the performance and productivity of the mission. However, the relevance and use of such SOPE early on during the Mission Design Phase (MDP) is not sufficiently recognised. As a result, science operations planning is often neglected or poorly assessed during the mission definition phases. This can result in mission architectures that are not optimum in terms of cost and scientific returns, particularly for missions that require a significant amount of science operations planning. Consequently, science operations planning difficulties and cost underestimations are often realised only when it is too late to design and implement the most appropriate solutions. In addition, higher costs can potentially reduce both the number of new missions and the chances of existing ones to be extended. Moreover, the quality, and subsequently efficiency, of SOPE can vary greatly. This is why we also believe that the best possible type of SOPE requires a structure similar to the ones of existing bodies of expertise dedicated to the data processing such as the International Planetary Data Alliance (IPDA), the Space Physics Archive Search and Extract (SPASE) or the Planetary Data System (PDS). Indeed, this is the only way of efficiently identifying science operations planning issues and their solutions as well as of keeping track of them in order to apply them to new missions. Therefore, this paper advocates for the need to allocate resources in order to both optimise the use of SOPE early on during the MDP and to perform, at least, a feasibility study of such a more structured SOPE.     

The geomagnetic solar flare effect identified by SIIG as an indicator of a solar flare observed by GOES satellites

This paper studies the efficiency of geomagnetic solar flare effects (gsfe) in X solar flare detection; so during the period 1999–2007 a comparison between solar flare (sf) observed by satellites of the Geostationary Operational Environmental Satellite (GOES) programme and gsfe published by the Service International des Indices Geomagnetiques (SIIG) is made.     

Mean energy of response to galactic cosmic ray spectrum: IMP 8 and Climax neutron monitor

Solar modulations of galactic cosmic ray (GCR) intensity contain a wealth of information about their transport in the heliosphere. To extract this information from the data one studies the dependence of the observed modulations on the mean energy of response of detectors providing data for the analyses. There is a great deal of confusion about the detector energy response to GCR spectrum in the literature. We present a preliminary report on the computations of the mean energy of response for the Climax neutron monitor (CL/NM) and IMP 8 cosmic ray nuclear composition instrument to GCR protons for 1973–1998, covering the solar cycles 21 and 22. We find that for penetrating proton channel on IMP 8 the mean energy changes by a factor of over two whereas for the neutron monitor the change is only 21%. However, the corresponding change for the computed modulation function is a factor of about 3.5.