دانلود رایگان مقاله انگلیسی یک تحقیق در مورد نیمکره جنوبی بارش های شهابی - الزویر 2018

Abstract.

Results are presented from a video-based meteoroid orbit survey conducted in New Zealand between Sept. 2014 and Dec. 2016, which netted 24,906 orbits from +5 to -5 magnitude meteors. 44 new southern hemisphere meteor showers are identified after combining this data with that of other video-based networks. Results are compared to showers reported from recent radar-based surveys. We find that video cameras and radar often see different showers and sometimes measure different semi-major axis distributions for the same meteoroid stream. For identifying showers in sparse daily orbit data, a shower look-up table of radiant position and speed as a function of time was created. This can replace the commonly used method of identifying showers from a set of mean orbital elements by using a discriminant criterion, which does not fully describe the distribution of meteor shower radiants over time.

5. Conclusions

Video-based orbit surveys detect many different meteoroid streams than the current radar-based surveys. 44 new southern hemisphere showers are reported here. At least 200 southern hemisphere showers still remain to be discovered in video-based surveys, if there are as many showers on the southern hemisphere as there are on the northern hemisphere.

The duration of shower activity and the extend of the radiant distribution are all captured better in a look-up table than in the list of average orbital elements of a given shower. Each shower entry in the IAU Working List of Meteor Showers ought to be linked to the trajectory and orbital data of the detected meteoroids on which the shower assignment was based.

Future efforts will be focused on improving the CAMS shower look-up table. The new CAMS data visualization tool has the ability to show what specific meteors were assigned to a given shower in the current look-up table for any given day in the year. Where improvements are needed, this table can be modified to correct possible mistaken identities, add newly identified showers, or to improve how a shower is separated from the sporadic background.