Determining the parameters of a local coordinate system with a non-standard longitude of the central meridian. Ways to improve the accuracy of determining parameters

Improving the accuracy of calculating the longitude of the axial meridian, the coordinates of the starting point and the height of the local coordinate system is achieved through introducing an intermediate coordinate system. The longitude of the axial meridian of the intermediate coordinate system is chosen equal to the approximate value of the longitude of the axial meridian of the local coordinate system. The difference in longitudes of the axial meridians of the state coordinate system and the intermediate coordinate system is known. The final value of the axial meridian`s longitude of the local coordinate system relative to the longitude of the axial meridian of the state coordinate system is calculated as the sum of two longitude differences. The first is the difference between the axial meridians of the local and the intermediate coordinate systems; the second is the difference in longitudes between the axial meridians of the intermediate and the state system. The residual errors of the mathematical apparatus for calculating the longitude of the axial meridian are less than 0.005 arc seconds. The proposed technology has been tested at real works.

Studys on the laws of Gauss projection for area distortion

In the regions which has high altitude and is far from central meridian, Gauss projection has bigger area distortion and becomes main factors which influences the accuracy of area measurement. Through researching in detail the area distortion in the three respects that from ground to reference ellipsoid surface from reference ellipsoid surface to Gauss plane and from Gauss plane to compensating level surface, this paper finds the laws of Gauss projection for area distortion, and draws one computation model on 2000 coordinates system. This has contributed to restrict the influence of Gauss projection and choose suitable central meridian and compensating level surface.

The Unusual Widespread Solar Energetic Particle Event on 2013 August 19: Solar origin, CME-driven shock evolution and particle longitudinal distribution

<p>Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey, and L1 spacecraft, spanning a longitudinal range of 222° in the ecliptic plane, observed an energetic particle flux increase. The widespread solar energetic particle (SEP) event was associated with a coronal mass ejection (CME) that came from a region located near the far-side central meridian from Earth's perspective. The CME appeared to consist of two eruptions, and was accompanied by a ~M3 flare as a post-eruption arcade, and low-frequency (interplanetary) type II and shock-accelerated type III radio bursts.</p><p>Aims: The main objectives of this study are two, disentangling the reasons of the different intensity-time profiles observed by MESSENGER and STEREO-A, longitudinally separated by only 15°, and unravelling the single solar source related with the SEP event.</p><p>Results: The solar source associated with the widespread SEP event is the shock driven by the two-stages CME, as the flare observed as a posteruptive arcade is too late to explain the estimated particle onset. The different intensity-time profiles observed by STEREO-A, located at 0.97 au, and MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering beyond Mercury's orbit. The longitudinal extent of the shock does not explain by itself the wide spread of particles in the heliosphere. The particle increase observed at L1 may be attributed to cross-field diffusion transport, and this is also the case for STEREO-B, at least until the spacecraft is eventually magnetically connected to the shock at ~0.6 au. The CME-driven shock may have suffered distortion in its evolution in the heliosphere, such that the shock flank overtakes the shock nose at 1 au.</p>

Mid-latitude effects of “expanded” geomagnetic substorms: a case study

The goal of this work is to examine the effects of the “expanded” or “high-latitude” substorms at mid-latitudes. These substorms are generated at auroral latitudes and propagate up to geomagnetic latitudes above ∼70° GMLat. They are usually observed during reccurent high-speed streams (HSS) from coronal holes. To identify the substorm activity, data from the networks IMAGE, SuperMAG and INTERMAGNET, and data from the all-sky cameras in Lovozero were used. To verify the interplanetary and geomagnetic conditions, data from the CDAWeb OMNI and from the WDC for geomagnetism at Kyoto were taken. We analyzed one substorm event on 20 February 2017 at ∼18:40 UT, it developed during HSS, in non-storm conditions. Some features of mid-latitude positive bays (MPB) at the European and Asian stations, and in particular at the Scandinavian meridian have been studied: the bay sign conversion from negative to positive values, the longitudinal and latitudinal extent of the MPB. The central meridian of the substorm was determined.

Determining the parameters of a local coordinate system with a non-standard longitude of the central meridian. Analysis of existing methods

Processing the results of topographic and geodetic works is performed in local coordinate systems. The parameters of the local coordinate systems were established on the basis of SK-42 or SK-63 systems. At present, it is necessary to set new communication parameters with coordinate systems SK-95 and GSK-2011. In many MCSs, the central meridians do not coincide with the origin, and the coordinates of the starting points were obtained from the catalogs of the preliminary calculation geodetic network. To establish the new communication parameters, it is necessary to determine the longitude of the central meridian MCS in SK-95 and GSK-2011 systems. To find the errors in calculating the longitude of the central meridian, MCS the models were constructed with different positions of the central meridian relative to the origin. The longitude was calculated using well-known and new formulas and methods. Errors in calculating the longitude of the MSC are systematic. An increase in the calculation volume does not exclude the influence of systematic errors, reaching 4ʺ. For some lines, they make 8ʺ.

A Comprehensive Study of Superstorms from 1957 to present

<p>We present a comprehensive study of all 39 superstorms (minimum Dst ≤ −250 nT) occurring from 1957 to present including analyzing their main phase developments, seasonal and solar cycle dependences, as well as their solar and interplanetary causes. We find that 87% of the superstorms have a multistep main phase development or are built upon preceding geomagnetic activities, and 90% of the superstorms occurred either near solar maximum or during the declining phase.  For the superstorm association with solar activities, 54% of the superstorms were associated with X‐class solar flares, 36% were associated with M‐class flares, and 5% with C‐class flares. All solar flares related to superstorms occurred in active regions, indicating the importance of active regions to superstorms. Most flares were located in the central meridian or slightly west of it as expected. For the interplanetary conditions leading to the development of the superstorm main phase, 95% of the 19 superstorms with available solar wind data are solely caused or partially caused by the sheath anti-sunward of an interplanetary coronal mass ejection (ICME), indicating the importance of the sheath structure in driving superstorms. For eight superstorms that have identifiable interplanetary shocks preceding the ICMEs, the shock normal angles were almost all quasi‐perpendicular. Larger shock normal angles statistically corresponded to greater superstorm intensities.</p>

Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH

Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about ${\pm}\, 60^{\circ}$±60∘, for which we derive sizes between $1.6 \times 10^{9}$1.6×109 and $1.8 \times 10^{11}\mbox{ km}^{2}$1.8×1011 km2. The absolute value of the mean signed magnetic field strength tends towards an average of $2.9\pm 1.9$2.9±1.9 G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes.

Harmonization of different type of coordinate systems used for North Macedonian official spatial data

<p><strong>Abstract.</strong> From the beginning of developing vector data sets in Macedonia, till now, three type of coordinate values for North Macedonian spatial data have been used.</p><p>Law for real estate cadaster and Regulation for basic geodetic works are the official legal bases for definition of official state coordinate system. In both legal documents, state coordinate system is defined by Ellipsoid of Bessel 1841, Datum of Hermannskogel, and Gauss-Kruger projection with central meridian 21&amp;deg;&amp;thinsp;E, scale factor 0.9999, false easting 500000&amp;thinsp;m, false northing 0&amp;thinsp;m and 7th projecting zone per 3&amp;deg;. Based on mentioned parameters, the coordinate systems EPSG 6204 and EPSG 6316 are defined and internationally recognized. The core deferens between them is false easting value. As a result of both coordinate systems parameters, the values of easting coordinates are far from each other for 7000&amp;thinsp;km!</p><p>Beside EPSG 6204 and 6316, official spatial data sets defined in CAD software were digitized by excluding first digits of easting and northing coordinates, by excluding digits 7 for easting and 4 for northing coordinates of spatial data.</p><p>Using three types of coordinate values, requires process of data harmonization before their usage in same project, in order to reach the spatial data overlapping. Third type of coordinate system, due to the lack of coordinate system parameters, can not be automatically overlapped with data defined in EPSG6204 and EPSG6316, which requires defining of intermediate coordinate system for third type of data in order to establish the mathematical base for data harmonization/overlapping by transformation of coordinates between three systems.</p>

Comparing extrapolations of the coronal magnetic field structure at 2.5R⊙with multi-viewpoint coronagraphic observations

The magnetic field shapes the structure of the solar corona, but we still know little about the interrelationships between the coronal magnetic field configurations and the resulting quasi-stationary structures observed in coronagraphic images (such as streamers, plumes, and coronal holes). One way to obtain information on the large-scale structure of the coronal magnetic field is to extrapolate it from photospheric data and compare the results with coronagraphic images. Our aim is to verify whether this comparison can be a fast method to systematically determine the reliability of the many methods that are available for modeling the coronal magnetic field. Coronal fields are usually extrapolated from photospheric measurements that are typically obtained in a region close to the central meridian on the solar disk and are then compared with coronagraphic images at the limbs, acquired at least seven days before or after to account for solar rotation. This implicitly assumes that no significant changes occurred in the corona during that period. In this work, we combine images from three coronagraphs (SOHO/LASCO-C2 and the two STEREO/SECCHI-COR1) that observe the Sun from different viewing angles to build Carrington maps that cover the entire corona to reduce the effect of temporal evolution to about five days. We then compare the position of the observed streamers in these Carrington maps with that of the neutral lines obtained from four different magnetic field extrapolations to evaluate the performances of the latter in the solar corona. Our results show that the location of coronal streamers can provide important indications to distinguish between different magnetic field extrapolations.

Warm and cool starspots with opposite polarities

Aims. We present a temperature and a magnetic-field surface map of the K2 subgiant of the active binary II Peg. Employed are high resolution Stokes IV spectra obtained with the new Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT). Methods. Fourteen average line profiles are inverted using our iMap code. We have employed an iterative regularization scheme without the need of a penalty function and incorporate a physical 3D description of the surface field vector. The spectral resolution of our data is 130 000 which converts to 20 resolution elements across the disk of II Peg. Results. Our main result is that the temperature features on II Peg closely correlate with its magnetic field topology. We find a warm spot (350 K warmer with respect to the effective temperature) of positive polarity and radial field density of 1.1 kG coexisting with a cool spot (780 K cooler) of negative polarity of 2 kG. Several other cool features are reconstructed containing both polarities and with (radial) field densities of up to 2 kG. The largest cool spot is reconstructed with a temperature contrast of 550 K, an area of almost 10% of the visible hemisphere, and with a multipolar magnetic morphology. A meridional and an azimuthal component of the field of up to ±500 G is detected in two surface regions between spots with strong radial fields but different polarities. A force-free magnetic-field extrapolation suggests that the different polarities of cool spots and the positive polarity of warm spots are physically related through a system of coronal loops of typical height of ≈2 R⋆. While the Hα line core and its red-side wing exhibit variations throughout all rotational phases, a major increase of blue-shifted Hα emission was seen for the phases when the warm spot is approaching the stellar central meridian indicating high-velocity mass motion within its loop. Conclusions. Active stars such as II Peg can show coexisting cool and warm spots on the surface that we interpret resulting from two different formation mechanisms. We explain the warm spots due to photospheric heating by a shock front from a siphon-type flow between regions of different polarities while the majority of the cool spots is likely formed due to the expected convective suppression like on the Sun.