Spectral characteristics of the quasi-biennial oscillation of total Ozone

The 12-month running means of the 50 hPa low latitude zonal wind and total ozone values for the latitude zones NP (North Polar), NT (North Temperate), TRO (Tropical), ST (South Temperate), SP (South Polar) were subjected to special analysis, separately over the two successive 18 year intervals, 1958-1975 and 1976-1993. In the interval 1958-1975, the wind had a prominent peak at 2.45 years and two smaller but significant peaks at 1.98 and 3.05 years. For ozone only NP. NT and ST had roughly similar peaks (2.37, 2.41, 2.48 years), while TRO and SP had different peaks (2.27 and 2.12 years). All ozone series had significant peaks at 20-21 months, barely significant in the wind series. Ozone peaks were noticed in the 3-5 years band also. In the interval 1976-1993, the patterns were different. The wind had only one prominent peak at 2.51 years. For ozone, NP, NT, ST had roughly similar peaks (2.41, 2.45, 2.45 years) while TRO. Speed different peaks (2.32 and 2.29 years). All ozone series had significant peaks at 20-22 months and in the 3-5 year band; but these were absent in the wind series. The 3-5 year band probably indicates ENSO effects. A cross-correlation analysis between wind and ozone showed that TRO maxima coincided with westerly wind maxima. while NT, ST and NT, NP were phase shifted by 4 and 6 seasons.

Revisiting the Distance to Radio Loops I and IV Using Gaia and Radio/Optical Polarization Data

Galactic synchrotron emission exhibits large angular scale features known as radio spurs and loops. Determining the physical size of these structures is important for understanding the local interstellar structure and for modeling the Galactic magnetic field. However, the distance to these structures is either under debate or entirely unknown. We revisit a classical method of finding the location of radio spurs by comparing optical polarization angles with those of synchrotron emission as a function of distance. We consider three tracers of the magnetic field: stellar polarization, polarized synchrotron radio emission, and polarized thermal dust emission. We employ archival measurements of optical starlight polarization and Gaia distances and construct a new map of polarized synchrotron emission from WMAP and Planck data. We confirm that synchrotron, dust emission, and stellar polarization angles all show a statistically significant alignment at high Galactic latitude. We obtain distance limits to three regions toward Loop I of 112 ± 17 pc, 135 ± 20 pc, and <105 pc. Our results strongly suggest that the polarized synchrotron emission toward the North Polar Spur at b > 30° is local. This is consistent with the conclusions of earlier work based on stellar polarization and extinction, but in stark contrast with the Galactic center origin recently revisited on the basis of X-ray data. We also obtain a distance measurement toward part of Loop IV (180 ± 15 pc) and find evidence that its synchrotron emission arises from chance overlap of structures located at different distances. Future optical polarization surveys will allow the expansion of this analysis to other radio spurs.

A Unified Model for the Fan Region and the North Polar Spur: A Bundle of Filaments in the Local Galaxy

We present a simple, unified model that can explain two of the brightest, large-scale, diffuse, polarized radio features in the sky, the North Polar Spur (NPS) and the Fan Region, along with several other prominent loops. We suggest that they are long, magnetized, and parallel filamentary structures that surround the Local arm and/or Local Bubble, in which the Sun is embedded. We show that this model is consistent with the large number of observational studies on these regions and is able to resolve an apparent contradiction in the literature that suggests that the high-latitude portion of the NPS is nearby, while lower-latitude portions are more distant. Understanding the contributions of this local emission is critical to developing a complete model of the Galactic magnetic field. These very nearby structures also provide context to help understand similar nonthermal, filamentary structures that are increasingly being observed with modern radio telescopes.

Photon boomerang in a nearly extreme Kerr metric

The Kerr rotating black hole metric has unstable photon orbits that orbit around the hole at fixed values of the Boyer-Lindquist coordinate r that depend on the axial angular momentum of the orbit, as well as on the parameters of the hole. For zero orbital axial angular momentum, these orbits cross the rotational axes at a fixed value of r that depends on the mass M and angular momentum J of the black hole. Nonzero angular momentum of the hole causes the photon orbit to rotate so that its direction when crossing the north polar axis changes from one crossing to the next by an angle I shall call ∆φ, which depends on the black hole dimensionless rotation parameter a/M = cJ/(GM2) by an equation involving a complete elliptic integral of the first kind. When the black hole has a/M ≈ 0.994 341 179 923 26, which is nearly maximally rotating, a photon sent out in a constant-r direction from the north polar axis at r ≈ 2.423 776 210 035 73 GM/c2returns to the north polar axis in precisely the opposite direction (in a frame nonrotating with respect to the distant stars), a photon boomerang.

DETECTING THE SOURCES OF ICE BLOCK FALLS AT THE MARTIAN NORTH POLAR SCARPS BY ANALYSIS OF MULTI-TEMPORAL HIRISE IMAGERY

We have developed a method for automatically detecting the sources of ice block falls at the Martian north polar scarps. Multitemporal red-filter High Resolution Imaging Science Experiment (HiRISE) images were processed by using the open source NASA Ames Stereo Pipeline in combination with the USGS Integrated Software for Imagers and Spectrometers to produce 0.25 m resolution images as well as a 1 m resolution DTM. The multi-temporal HiRISE images were firstly ortho-rectified by the DTM, and then co-registered by using the Enhanced Correlation Coefficient Maximization (ECC) algorithm. We applied the change detection method on the well-aligned sub-meter scale HiRISE images, which were taken in Mars Year 29 and Mars Year 30, to investigate mass wasting at the scarp area centred at 85.0°N, 151.5°E. The idea of the change detection method is to identify changing shadow patterns based on the grayscale difference between the images. The final results show that erosion events occurred at the full length of this study’s scarp within one Mars Year. However, only the upper and lower part of the scarp show erosion activity, whereas the intermediate parts seem inactive, and this correlates with the slope.

The Northern Sea Route in Political and Economic Frame of Reference in the 17th and Early 20th Century

The article considers the influence of economic and political factors on development of the state policy on the Northern Sea Route and its effective use. The success that Russia reached in the foreign policy, has determined the cautiousness or openness of its actions in the Arctic Seas. The article briefly describes the navigational and hydrographical traffic conditions in the Arctic Seas, the dangerous areas for sailing are noted in the text, as well as the new attempts that Russia made to establish navigation in the area. The intense activity in the North Polar Region, including research activity, was determined by economic interests, such as opportunities for maritime trade and transport routes development, as well as political interests, which include defense of own territories and development of new lands. The research is based on valuable sources of information on the North Polar Region, one of which is European and Russian geographical maps of the18th and 19th centuries, which managed to cover many blank spots, that resulted in delineating a clearer Arctic shoreline of Russia. Although the Northern Sea Route could hardly become a major transport channel due to the severe natural conditions, Russia tried to sustain its influence and defend its territories, especially when real threats to its national interests in the Arctic region arose.