Centennial variations in sunspot number, open solar flux and streamer belt width: 3. Modelling

From the variation of near-Earth interplanetary conditions, reconstructed for the mid-19th century to the present day using historic geomagnetic activity observations, Lockwood and Owens [2014] have suggested that Earth remains within a broadened streamer belt during solar cycles when the Open Solar Flux (OSF) is low. From this they propose that the Earth was immersed in almost constant slow solar wind during the Maunder minimum (c. 1650-1710). In this paper, we extend continuity modelling of the OSF to predict the streamer belt width using both group sunspot numbers and corrected international sunspot numbers to quantify the emergence rate of new OSF. The results support the idea that the solar wind at Earth was persistently slow during the Maunder minimum because the streamer belt was broad

Quantifying the latitudinal representivity of in situ solar wind observations

Advanced space-weather forecasting relies on the ability to accurately predict near-Earth solar wind conditions. For this purpose, physics-based, global numerical models of the solar wind are initialized with photospheric magnetic field and coronagraph observations, but no further observation constraints are imposed between the upper corona and Earth orbit. Data assimilation (DA) of the available in situ solar wind observations into the models could potentially provide additional constraints, improving solar wind reconstructions, and forecasts. However, in order to effectively combine the model and observations, it is necessary to quantify the error introduced by assuming point measurements are representative of the model state. In particular, the range of heliographic latitudes over which in situ solar wind speed measurements are representative is of primary importance, but particularly difficult to assess from observations alone. In this study we use 40+ years of observation-driven solar wind model results to assess two related properties: the latitudinal representivity error introduced by assuming the solar wind speed measured at a given latitude is the same as that at the heliographic equator, and the range of latitudes over which a solar wind measurement should influence the model state, referred to as the observational localisation. These values are quantified for future use in solar wind DA schemes as a function of solar cycle phase, measurement latitude, and error tolerance. In general, we find that in situ solar wind speed measurements near the ecliptic plane at solar minimum are extremely localised, being similar over only 1° or 2° of latitude. In the uniform polar fast wind above approximately 40° latitude at solar minimum, the latitudinal representivity error drops. At solar maximum, the increased variability of the solar wind speed at high latitudes means that the latitudinal representivity error increases at the poles, though becomes greater in the ecliptic, as long as moderate speed errors can be tolerated. The heliospheric magnetic field and solar wind density and temperature show very similar behaviour

On the origin of otho-gardenhose heliospheric flux

Parker-spiral theory predicts that the heliospheric magnetic field (HMF) will have components of opposite polarity radially toward the Sun and tangentially antiparallel to the solar rotation direction (i.e., in Geocentric Solar Ecliptic (GSE) coordinates, with Bx/By 0 which is frequently observed. We here study the occurrence and structure of OGH flux, as seen in near-Earth space (heliocentric distance r = 1 AU) by the Wind and Advanced Composition Explorer (ACE) spacecraft (for 1995 – 2017, inclusive) and by the Helios-1 and -2 spacecraft at 0.29 AU < r ≤ 1 AU (for December 1974 to August 1981), in order to evaluate the contributions to OGH flux generation of the various mechanisms and factors that are not accounted for by Parker-spiral theory. We study the loss of OGH flux with increasing averaging timescale T between 16 seconds and 100 hours and so determine its spectrum of spatial/temporal scale sizes. OGH flux at Earth at sunspot minimum is shown to be more common than at sunspot maximum and caused by smaller-scale structure in the HMF (with a mode temporal scale at a fixed point of Tmp of about 10hours compared to Tmp of about 40hours for sunspot maximum, corresponding to about 5.5 and 22 degrees (respectively) of heliocentric angular width for co-rotational motion or 21 Rs and 84 Rs for radial solar-wind flow (where Rs is a mean solar radius). OGH generated by rotating the HMF through the radial direction is also shown to differ in its spectrum of scale sizes from that for OGH generated by rotating the HMF through the tangential direction – the former does not contribute to the “excess” open heliospheric flux at a given r but the latter does. We show that roughly half of the HMF deflection from the ideal Parker-spiral needed to give the observed occurrence of OGH at Earth occurs at r below 0.3 AU. By comparing the Helios and near-Earth data we highlight some questions that can be addressed by the Parker Solar Probe mission which will study the HMF down to r = 0.046 AU. We suggest that with decreasing heliocentric distance, Probe will detect decreased OGH field due to draping around transient ejecta, such as blobs and coronal mass ejections, but increasing structure in the radial field within traditional HMF sectors that are remnant Alfvénic disturbances in outflow regions from coronal reconnection sites

Radial evolution of sunward strahl electrons in the inner heliosphere

The heliospheric magnetic field (HMF) exhibits local inversions, in which the field apparently “bends back” upon itself. Candidate mechanisms to produce these inversions include various configurations of upstream interchange reconnection; either in the heliosphere, or in the corona where the solar wind is formed. Explaining the source of these inversions, and how they evolve in time and space, is thus an important step towards explaining the origins of the solar wind. Inverted heliospheric magnetic field lines can be identified by the anomalous sunward (i.e. inward) streaming of the typically anti-sunward propagating, field aligned (or anti-aligned), beam of electrons known as the “strahl”. We test if the pitch angle distribution (PAD) properties of sunward-propagating strahl are different from those of outward strahl.We perform a statistical study of strahl observed by the Helios spacecraft, over heliocentric distances spanning ≈ 0.3 – 1 AU. We find that sunward strahl PADs are broader and less intense than their outward directed counterparts; particularly at distances 0.3 – 0.75 AU. This is consistent with sunward strahl being subject to additional, path-length dependent, scattering in comparison to outward strahl.We conclude that the longer and more variable path from the Sun to the spacecraft, along inverted magnetic field, leads to this additional scattering. The results also suggest that the relative importance of scattering along this additional path length drops off with heliocentric distance. These results can be explained by a relatively simple, constant-rate, scattering process

Tests of sunspot number sequences: 4. Discontinuities around 1946 in various sunspot number and sunspot group number reconstructions

We use five test data series to search for, and quantify, putative discontinuities around 1946 in five different annual-mean sunspot-number or sunspot-group number data sequences. The data series tested are: the original and new versions of the Wolf/Zurich/International sunspot number composite [RISNv1 and RISNv2] (respectively Clette et al., Adv. Space Res., 40, 919, 2007 and Clette et al., in “The Solar Activity Cycle”, 35, Springer, 2015); the corrected version of RISNv1 proposed by Lockwood, Owens, and Barnard (J. Geophys. Res. Space Physics, 119, 5193, 2014a) [RC]; the new “backbone” group number composite proposed by Svalgaard and Schatten (Solar Physics, 2016) [RBB]; and the new group-number composite derived by Usoskin et al. (Solar Physics, 2016) [RUEA]. The test data series used are: the group number [NG] and total sunspot area [AG] from the Royal Observatory, Greenwich / Royal Greenwich Observatory (RGO) photoheliographic data; the Ca K index from the recent re-analysis of Mount Wilson Observatory (MWO) spectroheliograms in the Calcium II K ion line; the sunspot-group number from the MWO sunspot drawings [NMWO]; and the dayside ionospheric F2-region critical frequencies measured by the Slough ionosonde [foF2]. These test data all vary in close association with sunspot numbers, in some cases non-linearly. The tests are carried out using both the “before-and-after” fit-residual comparison method and the correlation method of Lockwood, Owens, and Barnard, applied to annual mean data for intervals iterated to minimise errors and to eliminate uncertainties associated with the precise date of the putative discontinuity. It is not assumed that the correction required is by a constant factor, nor even linear in sunspot number. It is shown that a non-linear correction is required by RC, RBB, and RISNv1, but not by RISNv2 or RUEA. The five test datasets give very similar results in all cases. By multiplying the probability distribution functions together we obtain the optimum correction for each sunspot dataset that must be applied to pre-discontinuity data to make them consistent with the post-discontinuity data. It is shown that, on average, values for 1932 - 1943 are too small (relative to later values) by about 12.3 % for RISNv1 but are too large for RISNv2 and RBB by 3.8 % and 5.2 %, respectively. The correction that was applied to generate RC from RISNv1 reduces this average factor to 0.5 % but does not remove the non-linear variation with the test data, and other errors remain uncorrected. A valuable test of the procedures used is provided by RUEA, which is identical to the RGO NG values over the interval employed

Heliospheric modulation of galactic cosmic rays during grand solar minima: past and future variations

Galactic cosmic ray flux at Earth is modulated by the heliospheric magnetic field. Heliospheric modulation potential, Φ, during grand solar minima is investigated using an open solar flux (OSF) model with OSF source based on sunspot number, R, and OSF loss on heliospheric current sheet inclination. Changing dominance between source and loss means Φ varies in- (anti-) phase with R during strong (weak) cycles, in agreement with Φ estimates from ice core records of 10Be concentration, which are in-phase during most of the last 300 years, but anti-phase during the Maunder Minimum. Model results suggest “flat” OSF cycles, such as solar cycle 20 result from OSF source and loss terms temporarily balancing throughout the cycle. Thus even if solar activity continues to decline steadily, the long-term drop in OSF through SC21 to SC23 may plateau during SC24, though reemerge in SC25 with the inverted phase relation

The evolution of inverted magnetic fields through the inner heliosphere

Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood.Parker Solar Probe has recently observed rapid, Alfvénic, HMF inversions in the inner heliosphere, known as ‘switchbacks’, which have been interpreted as the possible remnants of coronal jets. It has also been suggested that inverted HMF may be produced by near-Sun interchange reconnection; a key process in mechanisms proposed for slow solar wind release. These cases suggest that the source of inverted HMF is near the Sun, and it follows that these inversions would gradually decay and straighten as they propagate out through the heliosphere. Alternatively, HMF inversions could form during solar wind transit, through phenomena such velocity shears, draping over ejecta, or waves and turbulence. Such processes are expected to lead to a qualitatively radial evolution of inverted HMF structures. Using Helios measurements spanning 0.3–1 AU, we examine the occurrence rate of inverted HMF, as well as other magnetic field morphologies, as a function of radial distance r, and find that it continually increases. This trend may be explained by inverted HMF observed between 0.3–1 AU being primarily driven by one or more of the above in-transit processes, rather than created at the Sun. We make suggestions as to the relative importance of these different processes based on the evolution of the magnetic field properties associated with inverted HMF. We also explore alternative explanations outside of our suggested driving processes which may lead to the observed trend

Galactic cosmic rays in the heliosphere

Simon R Thomas, Mathew J Owens and Mike Lockwood discuss how neutron monitor counts can help map space weather. This won the 2014 Rishbeth Prize for the best student talk at the Hot Spring MIST Meeting in Bath, April 2014

System for creating at a site, remote from a sterile environment, a parenteral solution

The present invention relates to a container, system, and method for creating parenteral solutions at a site, remote from sterile environments. The system includes a flexible container that is empty except for a prepackaged amount of a solute that is housed in the interior of the container. The container includes at least one port and a sterilizing filter in communication with an interior of the port. The container is so constructed and arranged that a fluid flow path is created from the port through the filter and into the interior of the container. A sterile water source including means for establishing fluid flow from the sterile water source into the port is provided. Accordingly, sterile water can flow from the sterile water source through the filter into the container where it is mixed with the solute to create a parenteral solution that can then be infused into a patient. A method and container are also provided

System for creating on site, remote from a sterile environment, parenteral solutions

The present invention provides a system and method for creating on site, remote from a sterile environment, parenteral solutions in large volume parenteral containers for intravenous administration to a patient. In an embodiment, this system comprises an empty large volume container including at least one port for accessing an interior of the container. The port includes a sterilizing filter for sterilizing a fluid fed through the port into the container. A second container is provided including a solute and having means for coupling the second container to the large volume container and thereby providing fluid communication therebetween allowing the solute to be received within the interior of the container. A sterile water source is also provided including means for placing the sterile water source in fluid communication with the port and allowing water to flow from the sterile water source into the interior of the container. This allows the solute, and sterile water that has been fed through the filter, to create a parenteral solution in the large volume parenteral container