A screen shot from the 16th of August 2016 - The Geminid Meteor shower putting on a display

The data from 2016 is incomplete and was captured during the calibration process undertaken when the LVST was set up. The data for the 2016 Perseid shower covers the period from the 4th to the 16th of August. Ideally a longer period from say the 25th July to the 25th of August would have better shown the increase and decrease in meteor activity to and from maximum.

August 2016 LVST Data: Summary of Observations and Interpretation of data analysis

Seasoned visual meteor hunters are used to scanning the sky in the early hours of the morning to see a handful of meteors between midnight and dawn. Meteor storms, in which literally hundreds of bright ‘shooting stars’ per hour fall from the sky, are at best, a once in a lifetime experience.

Once the LVST went on line in 2016, all members of the Jodrell Plank Observatory Team and Comet the Observatory cat were amazed by the constant level of meteor activity being detected by the very basic equipment being employed.

Over a period from the 4th to the 16^th of August 2016, the amount of data generated by the LVST was quite astonishing – 32,800 reflection observations were recorded.

In order to better investigate the ‘Perseid Shower’ meteor trail reflections, separating shower data from the constant background level of non-shower associated activity became a priority. As the 2016 Perseid shower data was the first to be analysed by the team, a number of iterative methods of enquiry were adopted to both test the efficacy of the procedure and the sensibility/validity of the results.

The Analytical Process Adopted

• Once extreme data outliers were removed, that is observations having a duration > than 720 cycles (approx 6 cycles =1 sec), what data remained was used as the source information data set containing 32,729 observations.
• With such a large data set, visual sorting of individual trails was determined impractical and statistical methods of filtering source data to create data subsets was adopted.
• The accepted classification of meteor trails was adopted ie. Separation of observations into Over dense O, Under dense U and Transition T trail observations.
• The source data set of all observations was then the U+O set (containing T)
• Following investigation (see page Separating U, O and T trail reflection observations), it was decided to use ‘duration of meteor trail’ as a measure by which to filter the U +O set to create a subset O-T. This contains meteor trails detected that have a duration = or > 18 cycles. This subset is likely to exclude 99% of U reflection observations but will include; Perseid shower trail O reflection observations, other shower trail reflections, sporadic meteor trail reflections and non meteor related noise.
• Filtering the O+U set by duration < 18 created a new subset U+T. This data subset is likely to contain all U and T reflection observations for all shower and non shower meteors and include some non meteor related noise.
• Detailed analysis of the U+T subset, see the graph logmaxpowerxduration (a Energy) plotted against Radial Velocity V, indicates a maximum value for log maxpowerxDuration =3.15 below which the standard deviation from the mean radial velocity suddenly increases.
• As T is the subset O of reflections that have short durations like U but similar velocity and power profiles to O, the Jodrell Plank Observatory Team decided to filter the U+O source data by log maxpowerxduration to leave only observations with a logmaxpowerxduration =>3.15. The new subset created is being interpreted as O+T.
• The relationships between the day date and the time on which observations were made for the O+T subset, particularly with regard to radial velocity and MaxpowerxDuration, were regarded as very useful in interpreting the meteor shower profile. The use of hexagonal binned data plots was considered effective in presenting a big picture view of a large data set.

Observations and Interpretations

Observations:

• General activity: (based on the largest data set O+U – 32,729 observations)
  • Overall activity reflection observations peaked at 4:00 UT on the 6th August 2016
  • Between the 4^th and 16^th August reflection observations were consistently higher between 0:00 and 17:00 UT than between 18:00 and 22:00 UT.
  • The mean radial velocity (Line of sight with the LVST) was +379 metres per sec with a standard deviation of 218.8.
• Shower activity: ( based on subsets of data O-T - 1547 observations and O+ T - 16950 observations)
  • O-T reflection observations peaked at 5:00 UT on the 10th August 2016.
  • Between the 4^th and 16^th August O-T reflection observations were consistently higher between 3:00 and 8:00 UT than at any other time and were very low between 12:00 and 22:00 UT.
  • The mean radial velocity of O-T reflection observations was +385.7 metres per sec with a standard deviation of 105.8.
  • O+T reflection observations peaked at approximately 18% between 2:00 and 8:00 UT and possibly at 5:00 UT on the 6^th August 2016. Between 11.62 and 12.6 % were recorded on the 10th of August. Between 10.4 and 11.34 % were recorded on the 7th of August. The minimum number of observations - between 2.92 and 3.44 % occurred on the 4th August.
  • The mean radial velocity for O+T reflection observations (Line of sight with the LVST) was +366.8 metres per sec with a standard deviation of 103.6.
  • For O+T set, on the 7th and 14^th of August, there were observations clustered around radial velocities (+109 and +69 m/sec respectively) significantly lower than the mean radial velocity for the O+T set.

Interpretations and Speculation:

• Activity associated with the 2016 Perseid Shower substantially commenced on the 5^th of August and reached its peak in the early hours of the 6^th of August. Activity remained high on the 7^th August but was falling to almost similar levels as had been experienced on the 4^th. The 8^th of August presented a rising level of activity which peaked on the 10^th of August at lower levels than had been experienced on the 7^th. Apart from a small rise in activity on the 14^th Aug, levels of activity fell back towards those experienced on the 4^th.
• The increase in reflection activity observed on the 14^th is not thought to be associated with the Perseid shower. This is conjecture based on observed differences in radial velocity ( and that meteors from showers take parallel paths) - By all accounts, Comet the cat finds this more difficult to swallow than Mr. Shrodinger's goldfish!
• The fluctuations in activity (ie. number of observations) are possibly proportional to the fluctuations in shower dust density. The Earth, in its annual path around the Sun, probably passed through the densest part of the dust from Comet Swift-Tuttle on the 6^th and 7^th of August 2016.
• The number of observations O-T having a duration =>3secs peaked on the 10^th of August between 4:00 and 5:00 UT. Enhanced activity was observed on the 6^th 9^th and 11^th although the number of observations was significantly lower than on the 10^th.
• The larger pieces of matter in the cometary stream stream, were probably encountered by the Earth on the 10^th of August. This hypothesis is based on a relatively small data sample of observations (O-T sub set -1547 reflections and associating increased reflection duration with increased meteoroid mass).
• The O+T data set contains reflection observations from at least one other meteor shower with increased activity being recorded after midday on the 7^th and 14^th of August. These observed reflections, sharing similar radial velocity and hours of the day, may be associated with the Capricornid, Alpha Capricornid or Delta Aquarid meteor showers which are active in July and August each year.

Comparing the reflection observations against radial velocity graphs for U+O, O-T and U+T:

• The O-T sub set of reflections is not only much smaller than the U+O set but also much smaller than the U+T sub set.
• The O-T sub set has a much lower SD (standard deviation from the mean) than either the full O+U set or the sub set U+T
• The sub sets were created by filtering the O+U set using an arbitrary value chosen for reflection duration.
• The U+O and U+T graphs show a consistent base level of observations across the full range of radial velocities (from -102 to +948 m/sec) underlying the 'Gaussian bell curve' of data that is centred on approx +379 m/sec). This base level set of observations warrants further analysis.